added grouped functionality to toggle

* Introduced new parameter called "group" to allow for grouped behaviour in toggling
 * The new behaviour allows for web developers to pass a group class or selector to identify the toggle grouping and to allow for only one of the toggled elements to hold a state.
 * Similar to the behaviour of a group checkbox list that only allows one element to be selected at a time.
 * @patheard I know you will probably play with this function a bit since it does the trick but not as flushed out as it should be. If you have a moment to play with it, that would be ideal

/cc @patheard