Re-wrote extension to consume new Guake D-Bus API methods
Changed gnome-shell dependency to 3.8 from 3.8.1 to permit wider use
Vastly reduced CPU usage by eliminating redundant label constructor from redraw() callback
Switched loop callback from timeout_add(200ms) to idle_add() as this seems to perform better without loading CPU
added github url to metadata.json
updated readme to include screenshot
fixed metadata.json issue that prevented enabling extension
1) Switched tab indices on labels from 0-based to 1+.  2) Resolved issue where tab redrawing loop would terminate after some minutes (albeit using nasty try/except loop).  3) Cleaned up some comments / other misc
Merge branch 'dbus_extras' (requisite API methods merged upstream in Guake project)