Updated the build process.

The build now tests for newer Python 3.x versions and PyPy.
Also the build will now test itself against Django 1.7RC1 instead of the latest beta version.
Updated the package's classifiers.
Added a note about PyPy support to the README file.
Merge pull request #70 from omerzimp/patch-1

Test Python 3.3, 3.4, and PyPy; test Django 1.7rc1