Fixes #387 - set id on init instead of each update
Fixes #376 - $asObject does not work with limit/startAt
Merge pull request #389 from firebase/release_0.8.1_idfix

Fixes #387 & #376 - set id on init instead of each update
Merged with master
Merge pull request #390 from firebase/release_0.8.1_defaults

Release 0.8.1 defaults
Merged with release_0.8.1