ENH: use suptitle to plot the title of a plot on faceting

On faceting, the title is addded to the figure and not to individual
axis which breaks on faceting.

See https://github.com/yhat/ggplot/issues/47#issuecomment-30340126
FIX: Make legends show up in ipyton notebook

This adds a workaround for a bug in the tight layout code in
matplotlib. The next version of matplotlib has the same fix
internaly, so this workaround is not needed for  matplotlib >1.3.1
https://github.com/matplotlib/matplotlib/issues/2530

Closes: yhat/ggplot#33
Merge pull request #164 from JanSchulz/various_fixes

Two fixes