Add a simple tox.ini for Astropy testing Python 2.6, 2.7, 3.2, and 3.3
Added some documentation for running the tests with tox
Added Cython to the dependencies
Merge pull request #774 from iguananaut/tox

Add a simple tox.ini for Astropy testing Python 2.6, 2.7, 3.2, and 3.3