new histogram syntax
Merge branch 'master' of https://github.com/plotly/graph-decoder

Conflicts:
	Examples.ipynb
	python-examples/basic-histogram.txt
	python-examples/contour-subplots.txt
	python-examples/overlaid-histogram.txt
	python-examples/shared-axes-subplots.txt
	python-examples/stacked-histogram.txt
	python-examples/style-bar.txt
	python-examples/style-histogram.txt
rm graph_reference