Merge pull request #1277 from aconley/comoving_volume_array

Allow comoving volume to accept arrays in non-flat case. Add unit test.
Conflicts:

	astropy/cosmology/core.py
	astropy/cosmology/tests/test_cosmology.py
Add changelog entry for #1277
Merge pull request #1279 from iguananaut/fits-test-issue

Fix minor issue in fhe io.fits tests