getting user identity from chrome store.
manifest.json ->
   key - copied from the manifest.json created in the application data directory. (this remains same and is attached to the api id).
   oauth2 -> authorisation scheme to get permission to access the user private data.
             client_id -> generated in google's developer console 'https://console.developers.google.com/project?authuser=0'.
             scope - the parameters here determine the various API access needed by the app.
             NOTE- the APIs like Google+ API should be enabled for this to work.
             individual scopes can be seen in developer console website.
   permissions: identity permission to enable the chrome.identity API and other sites permission (copied from the sample_chrome_apps 'Identity').

Created a dummy method to ask the user's consent (interactive = true) to get the desired information.
updated CSP to whatever will be internally used by the chrome app.
(see https://developer.chrome.com/apps/contentSecurityPolicy for more details)

sending an ajax call to google+ api to get user email id.
merging updates from master.
some progress for leaderboards.
added a leaderboard and completed dummy leaderprovider for testing.
created leader provider which uses the google app engine.

Initial version: need to be refactored.
still need to be
identity_helper.js --> to get the gmail id (user consent).

leaderboard.js --> show at max 3 leaders. leaderboard update only when username is available.
                   leaderboard update only when best score.

game_controller.js --> fixed bug. best score was not stored properly.

overall changes to publish appropriate events at appropriate time.
leader-board is now always visible.
beautified the leader-board a little.
changed level 7 as it was a duplicate.
merged update from chrome app branch.