Parse the object before set to allow for setting the priority on $set.

I was wanting to $set an object and pass the $priority. When doing this currently you get the following error: "Error: Firebase.set failed: First argument contains an invalid key ($priority).  Keys must be non-empty strings and can't contain ".", "#", "$", "/", "[", or "]" "

Looking at the code it looks like you set up a function for striping the keys that start with $ and setting the priority. Using this function I can now call $set and update/add $priority.