added contributing guide, although I have absolutely no idea why contributing.md is always ignored

- added contributing guide from:
  https://ulhpc-tutorials.readthedocs.io/en/latest/contributing/
- I have absolutely no idea why it is always ignored when the
  file is named contributing.md

help/contrib.md

+# Proposing a new tutorial / Contributing to this repository
+
+You're using a specific software on the UL HPC platform not listed in the above list? Then most probably you
+
+1. developed a set of script to effectively run that software
+2. used to face issues such that you're aware (eventually unconsciously) of tricks and tips for that specific usage.
+
+Then your inputs are valuable for the other users and we would appreciate your help to complete this repository with new topics/entries.
+
+To do that, the general approach is similar to the one proposed by [Github via the Forking procedure](https://help.github.com/articles/fork-a-repo/).
+Since we use [git-flow](https://github.com/nvie/gitflow), your workflow for contributing to this repository should typically involve the following steps:
+
+1. [Fork it](https://help.github.com/articles/fork-a-repo/)
+2. Initialize your local copy of the repository (including git submodules etc.): `make setup`
+2. Create your feature branch: `git flow feature start <feature_name>`
+3. Commit your changes: `git commit -am 'Added some feature'`
+4. Publish your feature branch: `git flow feature publish <feature_name>`
+5. Create new [Pull Request](https://help.github.com/articles/using-pull-requests/)
+
+More details are provided below.
+
+## git-flow
+
+The Git branching model for this repository follows the guidelines of [gitflow](http://nvie.com/posts/a-successful-git-branching-model/).
+In particular, the central repo (on `github.com`) holds two main branches with an infinite lifetime:
+
+* `production`: the *production-ready* tutorials
+* `devel`: the main branch where the latest developments interviene. This is the *default* branch you get when you clone the repo.
+
+## New tutorial layout
+
+So assuming you have [forked this repository](https://help.github.com/articles/fork-a-repo) to work freely on your own copy of it, you can now feed a new tutorial, assuming you follow the below guidelines.
+
+### Directory Layout
+
+```
+<topic>/<name>  # Select the appropriate root directory
+├── README.md              # Main tutorial file, in Markdown
+├── index.md -> README.md  # Symlink (for mkdocs)
+├── slides.pdf             # Slides proposing an overview of the tutorial
+├── cover_slides.png       # Picture of the cover of the slide
+├── Makefile               # GNU Makefile offering the targets 'fetch', 'compile', 'run' and 'plot'
+├── plots                  # Directory hosting the Gnuplots / R plots data
+├── runs/                  # Directory hosting the data/logs of the runs
+├── scripts/               # Eventually, a directory hosting some specific scripts
+└── launcher-<name>.{slurm|oar}.sh # launcher script to be used in the tutorial
+
+# Prepare the appropriate link for ReadtheDocs -- if needed
+docs/<topic> -> ../<topic>
+# such that 'docs/<topic>/<name>' points to '../<topic>/<name>'
+```
+
+You SHOULD  stick to a single `README.md` file, (using the [markdown](http://github.github.com/github-flavored-markdown/) format) if possible.
+
+Kindly follow the following format for this file (adapt `path/to` accordingly):
+
+```
+[![By ULHPC](https://img.shields.io/badge/by-ULHPC-blue.svg)](https://hpc.uni.lu) [![Licence](https://img.shields.io/badge/license-GPL--3.0-blue.svg)](http://www.gnu.org/licenses/gpl-3.0.html) [![GitHub issues](https://img.shields.io/github/issues/ULHPC/tutorials.svg)](https://github.com/ULHPC/tutorials/issues/) [![](https://img.shields.io/badge/slides-PDF-red.svg)](https://github.com/ULHPC/tutorials/raw/devel/path/to/slides.pdf) [![Github](https://img.shields.io/badge/sources-github-green.svg)](https://github.com/ULHPC/tutorials/tree/devel/path/to/) [![Documentation Status](http://readthedocs.org/projects/ulhpc-tutorials/badge/?version=latest)](http://ulhpc-tutorials.readthedocs.io/en/latest/path/to/) [![GitHub forks](https://img.shields.io/github/stars/ULHPC/tutorials.svg?style=social&label=Star)](https://github.com/ULHPC/tutorials)
+
+# <the title>
+
+      Copyright (c) 2013-2018 [You name,] UL HPC Team  <hpc-sysadmins@uni.lu>
+
+[![](https://github.com/ULHPC/tutorials/raw/devel/path/to/cover_slides.png)](https://github.com/ULHPC/tutorials/raw/devel/path/to/slides.pdf)
+
+The objective of this tutorial is to cover XXX, in particular:
+
+* objective 1
+* objective 2
+
+--------------------
+## Pre-requisites ##
+
+Ensure you are able to [connect to the UL HPC clusters](https://hpc-docs.uni.lu/connect/access/)
+In particular, recall that the `module` command **is not** available on the access frontends.
+
+Now you'll need to pull the latest changes in your working copy of the [ULHPC/tutorials](https://github.com/ULHPC/tutorials) you should have cloned in `~/git/github.com/ULHPC/tutorials` (see ["preliminaries" tutorial](../../preliminaries/))
+
+``` bash
+(access)$> cd ~/git/github.com/ULHPC/tutorials
+(access)$> git pull
+```
+
+Now **configure a dedicated directory `~/tutorials/<topic>` for this session**
+
+``` bash
+# return to your home
+(access)$> mkdir -p ~/tutorials/<topic>
+(access)$> cd ~/tutorials/<topic>
+# create a symbolic link to the reference material
+(access)$> ln -s ~/git/github.com/ULHPC/tutorials/<path> ref.d
+```
+
+**Advanced users** (_eventually_ yet __strongly__ recommended), create a [Tmux](https://github.com/tmux/tmux/wiki) session (see [Tmux cheat sheet](https://tmuxcheatsheet.com/) and [tutorial](https://www.howtogeek.com/671422/how-to-use-tmux-on-linux-and-why-its-better-than-screen/)) or [GNU Screen](http://www.gnu.org/software/screen/) session you can recover later. See also ["Getting Started" tutorial ](../../beginners/).
+
+``` bash
+# /!\ Advanced (but recommended) best-practice:
+#     Always work within a TMux or GNU Screen session named '<topic>' (Adapt accordingly)
+(access-aion)$> tmux new -s HPC-school   # Tmux
+(access-iris)$> screen -S HPC-school     # GNU Screen
+#  TMux     | GNU Screen | Action
+# ----------|------------|----------------------------------------------
+#  CTRL+b c | CTRL+a c   | (create) creates a new Screen window. The default Screen number is zero.
+#  CTRL+b n | CTRL+a n   | (next) switches to the next window.
+#  CTRL+b p | CTRL+a p   | (prev) switches to the previous window.
+#  CTRL+b , | CTRL+a A   | (title) rename the current window
+#  CTRL+b d | CTRL+a d   | (detach) detaches from a Screen -
+# Once detached:
+#   tmux ls  | screen -ls : list available screen
+#   tmux att | screen -x  : reattach to a past screen
+```
+
+Let's get an interactive jobs:
+
+```bash
+### Access to ULHPC cluster (if not yet done)
+(laptop)$> ssh aion-cluster    # or iris-cluster
+### Have an interactive job
+# ... either directly
+(access)$> si [...]
+# ... or using the HPC School reservation 'hpcschool'if needed  - use 'sinfo -T' to check if active and its name
+# (access)$> si --reservation=hpcschool [...]
+(node)$>
+```
+
+-----------------
+## Objective 1 ##
+
+instructions
+
+-----------------
+## Objective 2 ##
+
+instructions
+
+## Useful references
+```
+
+
+Remember that they shall be understandable for users having no or very few knowledge on your topic!
+
+One _proposal_ to organize the workflow of your tutorial:
+
+* Select a typical sample example that will be used throughout all the tutorial, that is easy to fetch from the official page of the software. Adapt the `make fetch` directive in your root `Makefile` to perform the corresponding actions.
+* (eventually) detail how to build the sources (using [EasyBuild](advanced/Easybuild). Adapt the `make build` accordingly.
+* dedicate a section to the running of this example in an _interactive_ job such that the reader has a better understanding of:
+   - the involved modules to load
+   - the classical way to execute the software
+   - etc.
+   Adapt also the `make run_interactive` accordingly
+* dedicate a second section to the running of the example in a _passive_ job, typically providing a generic launcher script adapted to your software. You might adapt / extend the [UL HPC launcher scripts](https://github.com/ULHPC/launcher-scripts) the same way to extend these tutorials. Adapt also the `make run` accordingly.
+* a last section would typically involves hints / elements to benchmark the execution, add tips/tricks to improve the performances (and see the effects of those improvements) and have a way to plot the results.  Adapt the `make plot` accordingly
+
+### Semantic Versionning
+
+The operation consisting of releasing a new version of this repository is automated by a set of tasks within the `Makefile` at the root of this repository.
+
+In this context, a version number have the following format:
+
+      <major>.<minor>.<patch>
+
+where:
+
+* `< major >` corresponds to the major version number
+* `< minor >` corresponds to the minor version number
+* `< patch >` corresponds to the patching version number
+
+Example: `1.2.0`
+
+The current version number is stored in the file `VERSION`. **DO NOT EDIT THIS FILE**, use the below primitives to affect the number it contains.
+For more information on the version, run:
+
+     $> make versioninfo
+
+If a new  version number such be bumped, you simply have to run:
+
+     $> make start_bump_{major,minor,patch}
+
+This will start the release process for you using `git-flow`.
+Then, to make the release effective, just run:
+
+     $> make release
+
+This will finalize the release using `git-flow`, create the appropriate tag and merge all things the way they should be.