Upgrade versions of ember, handlebars, and minMimosaVersion

Only changed enough so this compiles and runs with the latest Mimosa changes for Ember. I think this could use some minor cleaning up though. There is a nested template but it isn't used (so I didn't bother configuring the `nameTransform` property) and another template with no content. The template names also aren't per Ember naming conventions (though they still work).