Update ORM.php

http://dev.kohanaframework.org/issues/4652

Also related to https://github.com/kohana/orm/pull/77
Merge pull request #83 from neo22s/patch-2

Update ORM.php
refs #4652
Refs #4750: Fixes API guide issue for count_relations
Merge pull request #85 from rjd22/3.3/bugfix/fix_docs_mistake_for_count_relations

Refs #4750: Fixes API guide issue for count_relations