Fix kwargs description in docstring
Merge pull request #549 from stevensons/root2mpl-docstring

Fix kwargs description in docstring
set sample histograms in __init__
Merge pull request #550 from ndawe/master

[MRG] HistFactory: set sample histograms in __init__
histfactory: rm make_model and make_models. Use make_workspace
Merge pull request #551 from ndawe/master

[MRG] histfactory: rm make_model and make_models. Use make_workspace
ratioplot template
add fill_value argument to Hist.divide
RatioPlot: set tick lengths
RatioPlot: draw horizontal lines in ratio pad
_limits_helper: don't raise ValueError and instead return reasonable values if min=max