Support top-level observable view models using notification from the binding context
Add comments about the new observable-view-model implementation.
Revert to my original implementation of "bindingsUpdater", which removes the need to change the binding provider.
Group template foreach tests together.
Make sure observable view models work with templates. Make sure $index is up-to-date when using observable view models. Try to avoid double curly brace in binding string (messes up jQuery-tmpl).

Remove support for temporary binding context when extending a child context. Instead, use new extendCallback parameter.
Fix the template $index test so it actually tests that $index is correctly set when the binding context is updated.
Merge pull request #485 from knockout/485-observable-view-model

support observable view models at both the root and child context level