Threejs model driver tests

Things remaining before this is ready for merge:
- [ ] Figure out how to load components when test document is loaded as a file (cannot access other files from file url)
- [ ] Test the tests to see if they are testing what I think they are testing
- [ ] Refactor tests to eliminate repeated code

@davideaster and @bcbarsness, I wanted to open this pull request to start the conversation.  @davideaster, as we discussed, I'm going to need your help with the first one above.