Added support for custom highligthers in Typeahead.

A couple of smaller fixes, which I'm less certain of:

* Removed forced colors on a.btn which seems to interfere with third-party
bootstrap themes.
* The bootstrap-responsive.css is now injected last to make it work in
Chrome. In particular,  on smaller screens, `TextBox` wouldn't resize and `ControlLabel` wouldn't break from the adjacent input field.

It might be of interest that I've been experimenting with third-party bootstrap themes, as opposed to only relying on the default one, and that could be the reason why I'm seeing problems that others have not.