Bug fix for attribute lattyp

The code on lines 814 and 784 had attribute self.wcs.lattype which raised an AttributeError. The class in question has attribute 

astropy.wcs.Wcsprm.lattyp

So I edited those two to reflect the name
added test for the attribute error I got prior
Merge branch 'master' of https://github.com/astrodsg/astropy

# By astrodsg_laptop (3) and astrodsg (1)
* 'master' of https://github.com/astrodsg/astropy:
  It gives a warning on this file that doesn't effect the main purpose of this code
  fixed test for pix2world, still needs a more rigorous test of this functionality
  added test for the attribute error I got prior
  Bug fix for attribute lattyp

Conflicts:
	astropy/wcs/tests/test_wcs.py