Django deprecated the u-prefixed versions of the gettext methods,

removing them in 4.0. Since we support Django 1.6 on up, it's important

to use the right import for the right version of Django.
This adds a new django_evolution.compat.translation module, which

imports the correct versions and provides them under the new names. All

code has been switched over to this.

All unit tests pass on all supported versions of Django and Python.