Merge pull request #13 from doublerebel/master

Syntax updates for Gnome 3.6
update: to be able to load with gnome 3.6
Merge pull request #14 from daroczig/master

finishing #13 (update metadata.js)
code cleanup
updated extension information in code
more code cleanup
Update for run in Gnome 3.8
Merge pull request #17 from marcosraimundo3/patch-1

Update for run in Gnome 3.8
updated metadata.json to only support gs 3.6 and 3.8