add tests to deepMapValues, error on mapValues
adding mapKeys and deepMapKeys
splitting out the map and deep map tests
deepMapKeys and deepMapValues now throw on non-obj
pulling test for non-obj into helper file
formatting for deepKeys test
making k/v use more clear for mapKeys
removing deepMapKeys to discuss in separate PR
Merge pull request #8 from Clever/add_map_keys

Add mapKeys