Many services/directives have to interact with the body element, and
each one has to write the same long code. The $ionicBody service
provides some useful methods to clean up and reduce redundant code.
If a menu was opened when navigating to a different view, it is
possible that the `menu-open` class was left on the body tag, which
disables the elements on the next side menu view. On side menu destroy,
ensure menu-open was removed from the body class.
