Adding contributing guidelines.

Includes license, workflow, and file formats sections.

CONTRIBUTING.md

@@ -0,0 +1,37 @@
+Contributing Boot Camp Material
+===============================
+
+Licenses
+--------
+
+See http://software-carpentry.org/license.html for the licenses covering
+Software Carpentry material. By contributing you are agreeing that
+Software Carpentry may redistribute your work under these licenses.
+
+Workflow
+--------
+
+Software Carpentry uses a development workflow similar to that of
+[AstroPy][] and many other open source projects. The AstroPy docs have
+excellent sections on:
+
+* [Getting started with git][astropy-git]
+* [Developer workflow][astropy-workflow]
+
+File Formats
+------------
+
+### Text
+
+Text documents should be in [Markdown][] format and compatible
+with [Redcarpet][], the engine GitHub uses to render Markdown.
+
+### Slides
+
+The preferred format for slide presentations is still to be determined.
+
+[AstroPy]: http://astropy.org
+[astropy-git]: http://astropy.readthedocs.org/en/latest/development/workflow/index.html#getting-started-with-git
+[astropy-workflow]: http://astropy.readthedocs.org/en/latest/development/workflow/development_workflow.html
+[Markdown]: http://daringfireball.net/projects/markdown/
+[Redcarpet]: https://github.com/vmg/redcarpet