hashspace-bootstrap Alert messages plugin

This is a plugin for alert messages, there are no tests for it yet, those will be added soon.
Sometimes the `transitionend` event is not raised, which means that the alert container is not removed from the dom. I think this is due to a strange behaviour of the `$getElement` method: sometimes it fails when the `$refresh` method is not implemented in the component. I tried adding $refresh: function () {}, and it seems to work fine.