Percentage Width Support

I've taken @justindujardin's work from #407 and merged it with the most recent version of the ``master`` branch.

There are still some outstanding todos, but this is going to land in Chosen this week.

- [x] Fix some issues in documentation that came from merging master
- [x] Fix issue with expanding text field on multi chosen with percentage width
- [x] Investigate whether or not we can support % width from style
- [x] @mlharvest reviews CSS changes
- [x] Click test