Remove dependency on six and enable sphinx tests on Python 3
Added sphinx build test and make it pass on Python 3
Implement @mdboom’s suggestion
Copy instead of symlink
Avoid warning due to matplotlib not being installed
Change encoding
Added a changelog entry for #90
Fixes #98 by supporting the new .egg download cache in setuptools 7.0 in the affected tests.
Fix test to not require copying the astropy_helpers package; fixed a misuse of pkgutil.get_importer in the build_sphinx command that *happened* to work because we were adding a sys.path entry named 'astropy_helpers'.  But really as written this was assuming astropy_helpers was a module name, not a sys.path entry.  pkgutil.get_loader returns the loader for a specific module.