[SPIKE] Ember 2.12

[GavinJoyce]

part of #462

Working on making the tests pass, currently 97 are passing and the rest are commented out:

To run locally:

• grunt develop
• load http://localhost:8000/tests/?notrycatch=true

TODO:

• make all tests pass
• run a codemod on tests to update to QUnit 2 style
• fix grunt test - likely due to QUnit upgrade
• fix CI (seems to have started failing recently - https://travis-ci.org/ebryn/ember-model/builds)
• fix Fatal error: grunt.util._.contains is not a function when running grunt develop
• update expectAssertion helper and uncomment tests that use it
• refactor
• address any low hanging deprecations
• can we split this PR up into smaller ones?

[GavinJoyce]

Closing in favour of #465