Added basic xkcd styling functionality.
Fixed the lack of TextProperties in the title.
Specified better the font to use in the xkcd styling.
Fixed imports in ggplot examples.
Fixed formatting of title when xkcd argument is passed.
Merge branch 'master' into xkcd
Fixed docstring default xkcd to False.
Merge pull request #495 from damianavila/xkcd

Basic xkcd support for mpl.