adding 404 for can.fixture.store.findOne when resource not found
fixing broken test
Merge branch 'fixture-findone-#803' of github.com:ekryski/canjs into store_findone_fix

Conflicts:
	util/fixture/fixture.js
Tests for missing fixture item...

when using Model.update and Model.destroy.
Merge branch 'store_findone_fix' into minor

Resolves #921. Thanks @ekryski !