Update methods to Firebase 2.0.x
Updated from Kato's feedback
Minor stylistic changes to `key()` rename
Merge pull request #452 from firebase/jw-key-polyfill

Update methods to Firebase 2.0.x
Renamed utils.getSnapshotKey() to utils.getKey()
Merge pull request #454 from firebase/jw-getKey-rename

Renamed utils.getSnapshotKey() to utils.getKey()
Merge branch 'master' into jw-login-v2