Backbone 0.9.10

This is a start, but incomplete, since there are still issues with `triggerCancellableEvent` (only used in jQuery UI?) and DeepModel. Hoping @powmedia can take over from here.

The main change is that Backbone's `Model#set` no longer calls `validate` by default unless you pass the `{ validate: true }` option. Since `Form#commit` is basically a pass-through to `Model#set`, I'm proposing we follow Backbone's pattern here and only do model-level validation if you pass the same `{ validate: true }` option to commit.

Note: currently `Form#validate` calls model-level validation regardless. Not really sure if this should be left alone or not.