Luv colorspace conversions

Adding XYZ <--> Luv, RGB <-->
Adding test functions to mirror Lab tests
Adding references regarding Lab and Luv spaces to docstring
Removing unneeded division checking code
renaming machineEps to eps to match convention
flake8-compliant formatting
Cleaning up docstrings
docstring changes to correctly format input/output, clarifying XYZ and reference white
Adding note for Luv colorspace to top docstring
Format color conversion docstrings.
Merge pull request #1 from stefanv/luv-colorspace

Format color conversion docstrings.
Fix ColorHistogram to work with Open File
Add coverall support
Execute coveralls without flags.
Change to test directory before running coveralls
Ignore setup. No need for tmp dir any longer.
Fix invocation of nosetests.
Merge pull request #819 from stefanv/coverall_support

Add coveralls support
Merge pull request #804 from tonysyu/viewer-color-hist-fix

Fix ColorHistogram to work with Open File
FIX: New versions of FreeImage report software as "I", not "ImageMagick ..."
Merge pull request #822 from JDWarner/fix_freeimage_metadata_test

FIX: New versions of FreeImage report software as "I", not "ImageMagick ..."