Allow charts to be displayed horizontally

Really handy when dealing with data sets that have wordy x-axis titles.

e.g.

this-is-a-long-title ################
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;short-title #######
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;shorter ############
