Refactor the adapter, tests and build process, upgrade to ED 10

Upgrade to Ember-Data beta.10

The adapter event subscribing to Firebase events now lives
in the afterPush hook instead of being scattered around the adapter.

Embedded processing has been refactored to recursively normalize embedded
records, bringing it more in line with the EmbeddedRecordsMixin(maybe we should
use it at some point), simplyfying the code and fixing several embedded related
bugs.

Tests are now more functional allowing for easier refactors.
Tests have been refactored, for easier reading/writing and less
interdependence.

Lots of new tests added

Grunt now watches for changes and rebuilds correctly

Various other fixes, refactors and cleanups.

fixes #129 fixes #103 fixes #124 fixes #121 fixes #94
should also fix, but lacking tests for  #114 #96 #59
Might be good to pass the callback here as well in case the user happened to attach a listener to this location outside of EmberFire (calling `ref.off()` with no callback removes all listeners at a location)

```
ref.off('value', theCallbackThatWasUsed)
```