pygit2 and colors

* Uses pygit2 if it's installed otherwise it falls back to git-python.
* Colored output for the rainbow and unicorn lovers via colorama.

![colorama](https://cloud.githubusercontent.com/assets/1388/3717716/8558ab82-162a-11e4-8d28-846c5fb5b201.png)
https://github.com/jirikuncar/invenio-kwalitee/blame/master/docs/cli.rst#L49-L66