options on child views and automatically accumulating _keys from superclasses

I added two more things I needed in my backbone-flat branch:

1. options when creating child views (I needed this for my Controls view that let you spin a 3d model around)
2. automatically accumulate _keys from superclasses. This makes it much more elegant to have a hierarchy of model classes. Each class contributes its own _keys, and the instantiated class will automatically accumulate all of its superclasses _keys attributes.