Add tests for CSS escape sequences. Closes #33

Tests culled from http://mathiasbynens.be/notes/css-escapes
and http://mathiasbynens.be/demo/html5-id

Only one test fails out of the box, `#\{\}{background:lime;}`, and is
commented out at the end.
Merge pull request #58 from brettstimmerman/test/css-escapes

Add tests for CSS escape sequences. Closes #33