wire up the tests to use the bower versions

It looks like the tests have been running with old versions of ember and ember-data - see [latest travis build](https://travis-ci.org/toranb/ember-data-django-rest-adapter/builds/35926847#L170).

This ties the tests to the library versions specified in `bower.json` and required some fixes to support up to beta.6:

- fix templates with tables - [ember 1.5 each helper check](http://emberjs.com/blog/2014/03/30/ember-1-5-0-and-ember-1-6-beta-released.html#toc_handlebars-each-helper-checks-markup)
- update errors test to match DS.Errors format - [DS.Errors added in beta5 ](https://github.com/emberjs/data/blob/master/CHANGELOG.md#ember-data-100-beta5-january-11-2014) and [DS.Errors docs](http://emberjs.com/api/data/classes/DS.Errors.html)

beta.7 shows 3 failing tests, 2 of which appear to be [fixed in beta.9](https://travis-ci.org/toranb/ember-data-django-rest-adapter/builds/35926847#L170), so I left it at beta.6.