Add .transitionStop() method

https://github.com/rstacruz/jquery.transit/pull/110

Squashed commit of the following:

commit 0a0086c96923dfa7ae437fba7a924020281a9f8e
Author: tblasv <tblasv7@gmail.com>
Date:   Thu Feb 14 19:43:35 2013 +0200

    fix .transitionStop

commit 098e7f1936f40475f1cf20bf949b4be3e08f2c10
Author: tblasv <tblasv7@gmail.com>
Date:   Mon Feb 11 01:58:31 2013 +0200

    add .transitionStop() method

    works like $.fn.stop( [clearQueue ] [, jumpToEnd ] )