Examine source code of Circles

{
  "theme": {
    "images": {
      "theme_frame": "header3.jpg"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Circles",
  "manifest_version": 2,
  "description": "Well... nothing Special.\nBut there will be more to come ;)"
}