* Move CONTRIBUTING.rst to top level
The CONTRIBUTING.rst doc contains a lot of useful information about the
not only contributing to the project but also some useful information
about project policy and conventions. But it's currently in a hidden
directory so that github ui will show it on a help menu. So unless you
know to click on that help menu or that it's hidding in the .github
directory you'll never see it. This commit addresses this by moving the
file to the repo root so it's more obvious where it is, and to not break
the github ui it symlinks the file to the .github directory.
* Move code of conduct and switch to md
* Convert CONTRIBUTING to markdown