Add a file describing how to contribute.

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644 (file)
index 0000000..5914fef
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,18 @@
+# Contributing to deal.II
+deal.II is a community project that lives by the participation of its members — i.e., including you! It is our goal to build an inclusive and participatory community so we are happy that you are interested in participating. This document partly duplicates some extra information on participating available [on the project website](https://www.dealii.org/participate.html).
+
+## Getting started with git and GitHub
+If you are new to using git or the GitHub platform you may find it helpful to review [lecture 32.8](http://www.math.tamu.edu/~bangerth/videos.676.32.8.html), which should be enough to help you get started with using GitHub or possibly contributing to the library itself.
+
+## Asking and answering questions about the library
+The deal.II community maintains an active mailing list hosted by google groups [here](https://groups.google.com/forum/#!forum/dealii). The mailing list is for questions about the library of all levels. For more information see the website page describing our mailing lists [here](https://www.dealii.org/mail.html).
+
+## Bug reports
+It is a great help to the community if you report any bugs in the library that you may find. We keep track of all open issues with the library [here](https://github.com/dealii/dealii/issues). If you can, please try to include a minimal failing example that can help us reproduce the problem.
+
+## Making changes to the library
+To make a change to deal.II you should create a *fork* (through GitHub) of the library and a separate *branch* (sometimes called a feature branch). You can propose that your branch be combined with the rest of the library by opening a *pull request*. This will give a chance for others to review your code. While this seems very formal, keeping all of the code review in one place makes it easier to coordinate changes to the library (and there are usually several people making changes to the library at once). This process is described at length in [lecture 32.8](http://www.math.tamu.edu/~bangerth/videos.676.32.8.html). Please do not hesitate to ask questions about the workflow on the mailing list if you are not sure what to do.
+
+Since deal.II is a fairly large project with lots of contributors we use a set of [coding conventions](https://www.dealii.org/developer/doxygen/deal.II/CodingConventions.html) to keep the style of the source code in the library consistent. This convention essentially consists of using `astyle` for indentation, camel case for classes, and lower case letters with underscores for everything else. If you are new to the project then we will work with you to ensure your contributions are formatted with this style, so please do not think of it as a road block if you would like to contribute some code.
+
+The library is licensed under the GNU Lesser General Public License; while you will retain copyright on your contributions, all changes to the core library must be provided under this common license.