Remove sub-elements

[AstraLuma]

Move the functions of the sub-elements to :host to reduce complexity. Keeps all the same API. As a benefit, elem.z = 5 works again.

I don't know how to set up a full polymer developer environment, nor do I have google's testing resources. I just hope this improves the usability and performance of it.

[googlebot]

Thanks for your pull request.

It looks like this may be your first contribution to a Google open source project, in which case you'll need to sign a Contributor License Agreement (CLA) at https://cla.developers.google.com/.

If you've already signed a CLA, it's possible we don't have your GitHub username or you're using a different email address. Check the information on your CLA or see this help article on setting the email on your git commits.

Once you've done that, please reply here to let us know. If you signed the CLA as a corporation, please let us know the company's name.

[AstraLuma]

Done.

[googlebot]

CLAs look good, thanks!