Use of image_comparison decorator in v0.4.x causes test error.

[esc24]

The use of the image_comparison decorator in test_mpl_integration.py causes:

======================================================================
ERROR: Failure: NameError (name 'image_comparison' is not defined)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/local/sci/lib/python2.7/site-packages/nose-1.1.2-py2.7.egg/nose/loader.py", line 390, in loadTestsFromName
    addr.filename, addr.module)
  File "/usr/local/sci/lib/python2.7/site-packages/nose-1.1.2-py2.7.egg/nose/importer.py", line 39, in importFromPath
    return self.importFromDir(dir_path, fqname)
  File "/usr/local/sci/lib/python2.7/site-packages/nose-1.1.2-py2.7.egg/nose/importer.py", line 86, in importFromDir
    mod = load_module(part_fqname, fh, filename, desc)
  File "/net/home/h06/ecamp/cartopy/lib/cartopy/tests/mpl/test_mpl_integration.py", line 189, in <module>
    @image_comparison(baseline_images=['pcolormesh_global_wrap1'])
NameError: name 'image_comparison' is not defined

as the decorator is not imported. I suggest modifying test_mpl_integration.py to use the ImageTesting decorator.

In addition, the image_comparison decorator is imported but not used in the following:

test_image_tiles.py
test_img_nest.py
test_shapely_to_mpl.py
test_caching.py
test_gridliner.py

[pelson]

Good spot. I wonder how this was working at all...

@esc24 : may I assign you?