Small fix to ConcentricCircles.set_colors()
Fix docs, only allow list or tuple
Fixed docs line, added tests
Tested tests
Merge pull request #138 from rkmaddox/fixconcirc

FIX: Allow more than just list as input to ConcentricCircles.set_colors()
ENH: Add keepdims
Merge pull request #141 from Eric89GXL/add-keep

ENH: Add keepdims.  LGTM.