Make element a computed property
Make computed properties wrap the last evaluated dependency.
The motivation for this is so that when a wrap dependency is
about to be set, its self value is already properly set.
It also reduces complexity in the data bindings, data values look
like regular javascript, don't need to think about returning
properties anymore.
Add more testing aroung childNodes bindings
Refactor tests to create models when initializing variables
Remove notification when a computed property is evaluated with an argument