Test using web-component-tester, change shadowRoot to Polymer's shadowRoots['ajax-form'], and update to Polymer 0.5.1

Firefox doesn't work yet for the WCT test's; the url gets passed wrong - but this could be something to do with my configuration.

This does add the requirement of WCT, which adds the requirement of Java. You can also spin up a tiny webserver, navigate to test/index.html, and run the tests in the browser manually. It's quite a bit faster than running wct.

Pull request resolves #23, closes #16, and (hopefully?) fixes #28 
This points at a locally install web-component-tester folder. 
[These instructions](https://github.com/PolymerLabs/seed-element/blob/master/test/basic-test.html) mention wct should be installed globally ( npm install -g web-component-tester )

The test project also puts all it's bower dependencies one folder up (same depth as the seed-element project itself)
https://github.com/PolymerLabs/seed-element/blob/master/.bowerrc

The seed-element test project that's up on PolymerLabs git seems to use a [bower dependency](https://github.com/PolymerLabs/seed-element/blob/master/bower.json#L25) to get to that [browser.js file](https://github.com/PolymerLabs/seed-element/blob/master/test/basic-test.html#L18).

https://github.com/PolymerLabs/seed-element/blob/master/test/basic-test.html

Wondering if this is causing any issues with my tests failing.