BUG: matplotlib.__version__ is unicode
see here: https://ci.appveyor.com/project/jreback/pandas/build/1.0.455/job/2avadnw54tpv3lob

so it appears that matplotlib changed the version string in 1.4.0 to be `unicode` (and not a string).
(to be honest I would call that a bug, separate issue).

BUT our tests now fail because of this, I guess

`str(matploblib.__version__) > LooseVersion('1.4.0')` is now necessary

weird

@TomAugspurger 
