use vendor/bootstrap/ instead of vendor/twitter-bootstrap/

I added the bootswatch bower component which depended on twitter bootstrap and before I knew it, I had 2 bootstrap installs in vendor, one in twitter-bootstrap (from the git submodule) and the other in bootstrap (thru bower).

This patch changes the path to vendor/bootstrap instead of vendor/twitter-bootstrap hopefully making integration easier.

P.S.: I'm not very familiar yet with all the cool conventions surrounding what I call the JavaScript revival era so feel extremely free to drop (on the floor) this patch if it doesn't belong. I'd like to understand why though. Thanks!