override addHasMany of JSONSerializer to include an array of ids when serializing a non-embedded has-many relationship. The default ember-data assumption is that the update of the relationship would take place in the other model, causing the JSONSerializer to not include the array of ids.

This modification preserves the behavior when embedded=always, but now includes the array of ids.
Merge pull request #31 from craigteegarden/missing-hasmany-array-on-commit

add failing test: when saved, a model with a hasmay relationship does no...