Added GPL v3 license

This will allow people to use this in their free software but prohibit use in proprietary software and prevent re-licensing.
Added contribution guide to README

This will set expectations for contributors and remind you of the
process as well.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	README.md
Merge pull request #2 from jeremysmitherman/master

Added GPL v3 license