Naughty integration and layout container widget for the progressbar and the textbox.

* pulseaudio.lua: Changed maximum possible volume increase to 100% as there is no visual feedback on the progressbar in case it goes above that.
* widget.lua: Added basic notifications through naughty.
* widget.lua: Added a container layout widget for both the progressbar and the textbox as the textbox wouldn't appear for me.

I might be missing something here, but for me the percentage text wouldn't show not matter what. Feel free to revert that part of the code if the text could be enabled in some other way.