Only test the parsing of options. Integration test can stay in Ember

This focuses our tests on what we really need to know here. The higher-level integration test should come with the Ember merge.

Addresses a few items:

* Whitelist of valid boolean values per the HTML5 spec
* Previous code ran for all nodes, this just for the first option child node
* Comments

TODO:

* [ ] IE8 returns `"selected"` as the value of `getAttribute("selected")`, even when there is no attribute. I'm going to look at the raw HTML of the template with a regex to see if any is specified, and use this as a signal that an auto-selection is in place.