clean up firebaseUtils

[jamestalmage]

I think we should just eliminate simple wrappers for core angular functions. It is just making the code harder to understand without adding any real benefits.

• [x] utils.defer ==> $q.defer
• [x] utils.reject ==> $q.reject
• [x] utils.resolve ==> $q.when
• [ ] utils.compile ==> $rootScope.$evalAsync
• [ ] utils.batch ==> $rootScope.$evalAsync
• [ ] utils.applyDefaults ==> angular.extend (not a wrapper, but provides identical functionality)

Also, we should eliminate functions that are only used once (and just inline the functionality we need).

• [ ] utils.wait - only used once inside of utils.debounce
• [ ] utils.dataKeys - only used in tests

Finally, for angularfire 2.0.0, we should drop support for outdated dependencies.

• [x] utils.promise and the Q polyfill ==> $q(fn) once we drop angular 1.2.x support
• [x] utils.getKey ==> ref.key() once we drop Firebase 1.x.x support

[jwngr]

These look great, James. Thanks for putting this list together. I'm not sure when Kato or I will have a chance to get to these, but we will gladly merge any PRs you keep sending our way.

[jamesdaniels]

Closing as stale.