Polymer/firebase-element — pull request #10 by secobarbital (2014-09-08 18:25:39+00:00)
Title: Update keys, data and dataReady when the data and/or location becomes null

1. When the location becomes null, the query should change to null, which will cause the data and dataReady to change to null and false, respectively
1. When the data becomes null, the keys should be set to []