Test for isWatching on length property of an object
Tests for watch methods on length properties
Test for unwatch methods on object length property
Merge pull request #2387 from realityendshere/watch-length-tests

Tests for Ember metal watch/unwatch on "length" properties
assertion to catch mixins being passed to Object.create
Merge pull request #2394 from dagda1/mixin-assert

assertion to catch mixins being passed to Object.create