Added the 'autoActivate' config option

This is more for v2.0.0 but basically this config option will allow consuming libraries like [JamesMGreene/jquery.zeroclipboard](https://github.com/JamesMGreene/jquery.zeroclipboard), jquery.zclip, etc. to handle the activation and deactivation of ZeroClipboard themselves rather than relying on our `mouseover`/`mouseout` handlers.