Fix revision number in README.md

The guides seems to be described as revision 12.
bump ember-source
Remove findByClientId() test sync
Records are now looked up via recordForReference()
Merge pull request #991 from tricknotes/fix-revision-in-readme

Fix revision number in README.md
Merge pull request #990 from tricknotes/bump-ember-source

bump ember-source
Merge pull request #993 from rupurt/remove-unused-test-stub

Remove findByClientId() test sync