#540 - Fix VSM actions button position.

For #540, this should fix issues 2 and 3, across all resolutions and all cases (that I know of), and the issue of #482. This switches back to absolute positioning, which is the right thing to do here (since the position is really the same, regardless of the other items around it).

The z-index change is a bit of a hack for what looks like a Chrome bug (manifested as #482). If you reduce the height of the browser window, then you'll see that the action bar comes above the material's (circular) element, without this z-index change. This doesn't happen in Firefox.