fix to ggplot.to_html to support notebooks

the .notebook() function no longer exists.
Also removed setting plot titles since it is not clear how these should
be set.
Updated iPython notebook examples

Fixes the bokehnotebook example to follow more closely the style of
"cars". Relies on previous commit (863e7ef4) to fix the ggplot example.
Merge pull request #33 from spencerogden/master

ggplot.to_html out of sync with latest changes?