Bokeh charts

OK, this is the Bokeh chart interface, at least the very beginning... there is a lot of thing to add... a lot of thins to refactor... 
Currently it is supporting histograms, bar, scatter charts. Grouped and stacked. Support OrderedDict and pandas object as inputs. And we support kwargs and chained methods.
we should probably make a `publish_notebook` helper function some time that wraps these details up.