+ angularjs 1.2.15

There is no CHANGELOG for 1.2.15, but it is hosted on [GCDN](https://developers.google.com/speed/libraries/devguide#angularjs) & on their front page.

I left out 2 files that aren't on GCDN: [angular-mocks.js](http://ajax.googleapis.com/ajax/libs/angularjs/1.2.15/angular-mocks.js) & [angular-scenario.js](http://ajax.googleapis.com/ajax/libs/angularjs/1.2.15/angular-scenario.js) (1.03MB); the CDN zip file doesn't have `.min` files & they seem like they're for testing.