Adding Image.normalize().  Need unit tests.
Fix docstring formatting.
Fix Image.normalize() channel arg and related handling.

Image.normalize() channel arg now defaults to None, and
calls library.MagickNormalizeImageChannel() if != None
Using string channel name for Image.normalize(channel)
Clean up docstrings to match ambient style.
Adding channel value checking per suggestion
Adding very simplistic test for Image.normalize()
Merge remote-tracking branch 'upstream/master' into add-normalize
Adding test for single channel normalization (normalize_channel())
Merge pull request #95 from inactivist/add-normalize

Add Image.normalize() support