Added events (open, opened, close, closed) for bootstrap-dropdown menu

Created by: hgezim

Added events for bootstrap-dropdown, namely open, close, opened, and closed. Wrote documentation as well as unit testing.

Ran unit tests and other limited testing on:

Mac: Chrome 23; FF 16, 17; Safari 6 Windows: Chrome 23; FF 16, 17; IE 9

Please merge my changes from feature/dropdown-effects into 2.2.2-wip.