Can't react to error events #45
Description
Unless I'm missing something pretty basic it looks like the errorHandler functionality isn't working and the error event doesn't get fired as intended, such as from a security rules policy violation when writing data.
As far as I can tell the problem is that when firebase core library invokes the error handler, this is not bound correctly (it's Window) and it can't find the Polymer fire method for events. It produces TypeError: undefined is not a function referring to this.fire() See the images below.
I put in a quick-n-dirty fix to make it call the fire method correctly, but for some reason I still can't get it to run my event handler even then.
More generally, I'm not sure how I can take certain actions only if a DB operation succeeded and didn't produce an error. There doesn't seem to be anything like a .success() function.
