Make WCS instances use WCSAxes if available
Added simple documentation
Added changelog entry [ci skip]
Added URL for more details on WCSAxes
Make comment into docstring as suggested by @mhvk
clean wcs tests
Spead up test_all_world2pix significantly with using only the image centre
adding back test
Rewrite Unit.__rmul__ and __rdiv__ to speed up array [*/] unit
Finish making cosmology member functions broadcast over redshifts.

  other functions that take single redshift inputs (lookback_time, age),
  and testing all the other ones work.
  dark energy model tests of broadcasting.
Update CHANGES.rst
Changed inline to __inline on msvc
Merge pull request #3195 from mdmueller/change-inline-msvc

Changed inline to __inline when building with MSVC
Merge pull request #3186 from bsipocz/wcs_speed_up_test

Speed up wcs test
Merge pull request #3194 from aconley/cosmo_broadcasting

Finish making cosmology member functions broadcast over redshifts.
Merge pull request #3191 from mhvk/unit-faster-q-init

Rewrite Unit.__rmul__ and __rdiv__ to speed up array [*/] unit
Added an overlooked contributor (Mihai Cara)
Warn on invalid WCS unit
CHANGES entry
Ensure that we don't install Python 2.7.9 on Travis (use 2.7.8 instead) otherwise we get certificate erros due to the changes to certificate verification in 2.7.9 (see PEP 476).