Python 3

This includes full Python 3 compatibility, and a rough testsuite to check that the changes work across python versions.

## Highlights

* Supports Python 2.6+
* Now only supports Django 1.5+ (due to Python 2.6 requirement), and runs tests on Travis against all supported python versions and Django versions. South is always presumed to be latest version
* Supports TravisCI (this fork's builds can be found https://travis-ci.org/jvc26/django-colorful)
* Added RegexValidator to all field objects
* Few minor PEP8 changes