fixed test for pix2world, still needs a more rigorous test of this functionality
Merge branch 'master' of https://github.com/astrodsg/astropy

* 'master' of https://github.com/astrodsg/astropy:
  added test for the attribute error I got prior

They were conflicts I with things I wrote. All good

Conflicts:
	astropy/wcs/tests/test_wcs.py