Race conditions

We've noticed in our usage of angular-cached-resource that in certain high latency situations where the user is still online, there are some race conditions that cause data discrepancies.
 
07a88cd099c9fd3013153184069369c39ba0edf5 addresses an issue where a resourceInstance is saved and while the data is being sent to the server, the resourceInstance is edited again on the client before the write has resolved from the server. In this case the "local" changes on the resourceInstance shouldn't be clobbered when the server eventually responds.