Run setup.py from within the same python interpreter using setuptools' sandboxing--this way we can capture test coverage properly
A further enhancement that enables coverage for most of astropy_helpers.git_helpers.update_git_devstr
setuptools_boostrap was removed; instead we can just import ah_bootstrap for the same effect
For some reason this is *required* on Python 3.3, where previously it was not.  I don't know why since the module's loader should presumably already know the module's name.  But so we must...
Add tox.ini to run the tests on Python 2.6, 2.7, 3.2, and 3.3 (3.1 is skipped due to flagging support from the various tools involved--all the more reason for us to start deprecating 3.1...