Removal of priority breaks apps using the current security rules with "Permission denied"

The security rules in
https://github.com/firebase/geofire-js/blob/master/examples/securityRules/rules.json
uses `getPriority()` to validate a location on write.

By removing priority in https://github.com/firebase/geofire-objc/commit/96f40431d0d0fe3aac66bc0302da6c9cf3ab2f58, the rules now return a "permission denied" on writing a location as the validation of `getPriority` fails.

Also a version bump would have been nice for this as this would have helped troubleshooting ;)