Since we use Git for source control, change text on webside accordingly. Fixes https://bugs.launchpad.net/mixxx/+bug/1206147
Redraw developmentcircle.png used on home page as vector for more easy future updates.
Set transparent background for new vector document. Useful when exporting as png. Make "temp background" layer visible when working on the document.
Update development circle diagram png used on http://www.mixxx.org/get-involved/. This needs to be updated with the most recent git workflow though.