This allows us to view the jasmine results since the components are
rendered off screen instead of blowing away the jasmine test runner.

This reverts commit d3a675d.

ReactFireMixin can be rather slow with many items causing many change
events which can trigger many rerenders. By using Immutable data
structures we can cheaply check the entire tree and only rerender the
components that have actually changed their data.

This patch makes bindAsObject bind an Immutable.Map to the specified
prop and bindAsArray bind an Immutable.List to the specified prop.

It also changes the tests to verify that the data returned is correct.

Finally, the patch adds a `boundVarsHaveUpdated` method that will
cheaply check for changed state in the bound state variables. It's
intended to be used in a more complex `shouldComponentUpdate` method.
Tests for the new method are added.

- Iterate over snapshots using `forEach` to retain order.
- Use OrderedMap instead of Map for bindAsObject

Immutable needs to be imported in environments that enforce that. This
changes the build to require Immutable appropriately, and lists it as a
dependency of the node module.

This allows us to later get a firebase reference to it and to get it's
priority, among other nice things.