This provides a more reliable way to determine that we are definitely imported from an astropy source checkout, by checking for a file .astropy-root that would only ever possibly exist in this case.  This is inessential though and can be removed if people want to get rid of this extra top-level file.
Actually this is better; we can put the special .astropy-root file under static/ so that it's not cluttering up the actual root.  But this is good enough for the desired purposes.
Add an explanation to .astropy-root
If extension modules need to be recompiled, automatically try running build_ext --inplace rather than just failing to import--very convenient.  At some point this should be extended to work for any extension module (rather than just using the utils._compiler heuristic) but that could be a little trickier
Fixed support on Python 3, and got rid of .astropy-root per https://github.com/astropy/astropy-helpers/issues/107#issuecomment-64282919
Add Ellipse2D model
Add Ellipse2D model formula
Add test for Ellipse2D model
Add Ellipse2D example
Removed Ellipse2D __init__
Add changelog entry [skip ci]
Removed a few spectral density equivalencies which do not make sense.
Make cosmology distance functions act like ufuncs.

* Change FLRW.comoving_distance and FLRW.absorption_distance
  to handle input arrays with shape.  This automatically propogates
  through to the other distance functions in FLRW.
* Add unit tests for this functionality
* This starts to address #1816, but not completely.
* Closes #3177
* There seems to be a 1-2% performance penalty for distance calculations
  caused by this change.
Adding unique method to table operations
adding test for table.unique
removing unused imports from table tests
adding documentation for table.unique
update CHANGES.rst
Add Changelog entry
clean wcs tests