Clean up test suite from 3.x.x upgrade

[jwngr]

As part of merging in #717 to upgrade to the Firebase 3.x.x SDK, we made a lot of testing changes and the test suite is now pretty unstable and does not pass in Travis. We need to clean things up in general and specifically focus on:

1. Defining a better tick() method to force the digest loop to update.
2. Make sure our promise chains are set up properly and that we are waiting for things properly. For example, this test does not wait for the Firebase set() to complete.
3. Make sure the e2e tests actually pass (e.g. the Todo app has two failing tests).

[juan-orca]

sounds good!!

[CyrusZei]

did you guys just finished the angularfire 2.0 ? I see that the version is 2.0 now ?

edit: never mind, just noticed "build:failing"

[jwngr]

Yes, version 2.0.0 of AngularFire has been released and you can see the change log here. This bug is tracking the build failures. We wanted to get the release out instead of waiting for us to tackle all the build failures which seemed more like testing issues than actual code issues.

[abeisgoat]

See #740 for first batch of improvements

[jwngr]

@AbeHaskins - I think we can close this one now that the tests are fast and run reliably. Please re-open if there was anything else you meant to do.