Fixed failing test on python3.

[pelson]

No description provided.

[pelson]

fixes #2075.

[mdboom]

Sorry -- I should have waited for Travis before merging this. It seems there's a new problem behind this:

======================================================================
ERROR: matplotlib.tests.test_colors.test_cmap_and_norm_from_levels_and_colors2
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/virtualenv/python3.2/lib/python3.2/site-packages/nose/case.py", line 198, in runTest
    self.test(*self.arg)
  File "/home/travis/virtualenv/python3.2/lib/python3.2/site-packages/matplotlib-1.3.x-py3.2-linux-x86_64.egg/matplotlib/tests/test_colors.py", line 166, in test_cmap_and_norm_from_levels_and_colors2
    for d_val, expected_color in sorted(cases.items()):
TypeError: unorderable types: str() < int()

If you can't get to this, I'll try to find a solution.

[mdboom]

Fixed by f966e4a