Fix PhpErrorException undefined index: id 

If you create an "after_insert" observer that manipulates the just-inserted data, the add_primary_keys_to_where() method call will throw an undefined index exception because _original is empty and _is_new is false. Fix by setting _original to _data immediately after insert.
Merge pull request #244 from benharold/fix_after_insert

Fix PhpErrorException undefined index: id