Add tests for Unicode-related #719
Add tests for Unicode-related #719

This commit includes seven tests for FacetGrid with different data frames
containing either one Unicode string as a column label or as values in
one grouping column.

Under Python 3.x, which has full Unicode support, all seven tests pass.
Under Python 2.7, all tests fail in FacetGrid.set_titles() in one of the
lines containing the instruction ```title = template.format(**args)```.

anntzer/seaborn,lukauskas/seaborn,mwaskom/seaborn,arokem/seaborn,phobson/seaborn,anntzer/seaborn,lukauskas/seaborn,phobson/seaborn,JWarmenhoven/seaborn,petebachant/seaborn,mwaskom/seaborn,oesteban/seaborn,sauliusl/seaborn,arokem/seaborn