Better home-assistant sidebar

I thought it would be nice if you could 2-way-collapse the sidebar in homeassistant frontend.
I don’t think it would be much of an effort (I’m trying to get into css/js a little more myself) to let the burger menu expand - collapse - hide this sidebar.

Could look like this:

Oh wow, I think this is already on its way (just discovered this PR): :smile:
https://github.com/home-assistant/home-assistant-polymer/pull/3325