Added a test to confirm that loading a record with RESTAdapter rails to fire didCreate with a materialised record
materialize id on record update and call didCommit after payload is processed
properly set isUpdating flag and trigger didUpdate event

Previously isUpdating flag was set to false before the record array was populated with new records from the adapter. We defer didUpdate event to the end of the run loop in the same manner we do with findQuery didLoad event.
expose `fetch` that return promises and remove LoadPromise
return a promises from the transactions
use transaction promise to resolve record saves
prevent additional post and puts for bulk commits with embedded types
better handling of http requests
Advanced errors handling
fix rest adapter test
fix resolveWith