Use this directive to force the angular.element library.  This should be
used to force either jqLite by leaving ng-jq blank or setting the name of
the jquery variable under window (eg. jQuery).
Since angular looks for this directive when it is loaded (doesn't wait for the
DOMContentLoaded event), it must be placed on an element that comes before the script
which loads angular. Also, only the first instance of `ng-jq` will be used and all
others ignored.