tests if plotting.hist passes kwargs to matplotlib.hist
pass kwargs of grouped_hist to matplotlib.hist

 - remove log param of grouped_hist (not needed)
 - added grid param to grouped_hist (passed by caller - don't want to hand to mpl)
Merge remote-tracking branch 'pprett/hist-kwargs'

* pprett/hist-kwargs:
  pass kwargs of grouped_hist to matplotlib.hist
  tests if plotting.hist passes kwargs to matplotlib.hist