Update karma configuration.

Commit summary:

* Set testFramework option in the `frameworks` variable.

  > In order to clear the deprecation warning, is is now necessary to define
  > the framework choice in its place.

* Add module.exports as karma now requires it.
* Fix log level definition.
* Properly use the module pattern, that way Karma behaves well.
* Set up the proper npm dependencies.
Add global Ember to JSHint in model template.
Update Ember path in karma.conf.js.
Merge pull request #104 from josemota/karma-update

Set testFramework option in the `frameworks` variable.
Merge pull request #109 from josemota/fix-lint-model-template

Add global Ember to JSHint in model template.