Update Bower configuration.

* Use Handlebars `~>1.1` (will allow everything `< 2.0`).
* Replace `ember-data-shim` with `ember-data`. @fivetanley had the Bower
 registry fixed so that `ember-data-shim` and `ember-data` both point
 to https://github.com/components/ember-data. (FYI - Sometime in the future we
 will be removing `ember-data-shim`.)