Adds support for uppercase color hex strings.  Fixes: http://goo.gl/2yFupW
Separated tween configuration and execution.
Adds CONTRIBUTING.md.
Refactored configuration. Updated documentation and semver.
Merge branch 'master' of git://github.com/unstoppablecarl/shifty into unstoppablecarl-master
Cleans up code and improves/fixes docs.