Rename requires files to standard names.

The python community groks requirements.txt and test-requirements.txt as
reasonably standard files. We should use those filenames to make our
information more discoverable.

Fixes bug 1179008

Change-Id: I50a7c46f880e4257fa31d7d322d7bf70b0f5d3a6
Add CONTRIBUTING file.

This adds a pointer to how to contribute. Also, github will show
this on the pull requests page, so having one of these is a friendly
way to let people know we don't use those.

Change-Id: I36829798adacb0f6b8144502baeff64ca84e32b6
Move tests into the novaclient package.

tests/__init__.py implies a package in the global namespace. These
tests are not global python tests, but rather tests for novaclient.

Change-Id: Ifeb8082aa010d15dddc9ae02e35589bc78ad48cc