Added my-element test.

This is a test to show the errors discussed in https://github.com/Polymer/polymer/issues/216

```
[platform (stable)]$ grunt test
Running "karma:platform" (karma) task
WARN [config]: config.configure() is deprecated, please use config.set() instead.
INFO [karma]: Karma v0.9.5 server started at http://localhost:9876/
INFO [launcher]: Starting browser Chrome
INFO [launcher]: Starting browser Firefox
INFO [Firefox 22.0.0 (Linux)]: Connected on socket id iCHrTuaSVCM9MYq3uCl_
INFO [Chrome 28.0.1500 (Linux)]: Connected on socket id bs1rExbgLMuEH1OeuCmA
Chrome 28.0.1500 (Linux) SLOW 0.695 secs: integration html/mdv-shadow.html
Firefox 22.0.0 (Linux) SLOW 1.358 secs: integration html/mdv-shadow.html
Chrome 28.0.1500 (Linux) my-element html/my-element.html FAILED
	Error: the string "Uncaught Error: Uncaught AssertionError: my-element element must have been created: expected undefined to equal true" was thrown, throw an Error :)
	    at Runner.fail (/home/southerd/devel/polymer/polymer-all/platform/node_modules/karma-mocha/lib/mocha.js:3786:11)
	    at Runner.uncaught (/home/southerd/devel/polymer/polymer-all/platform/node_modules/karma-mocha/lib/mocha.js:4059:8)
	    at uncaught (/home/southerd/devel/polymer/polymer-all/platform/node_modules/karma-mocha/lib/mocha.js:4089:10)
Firefox 22.0.0 (Linux) SLOW 0.502 secs: styling html/styling/host.html
Firefox 22.0.0 (Linux) my-element html/my-element.html FAILED
	the string "Error: my-element element must have been created: expected undefined to equal true" was thrown, throw an Error :)
	Runner.prototype.fail@/home/southerd/devel/polymer/polymer-all/platform/node_modules/karma-mocha/lib/mocha.js:3786
	Runner.prototype.uncaught@/home/southerd/devel/polymer/polymer-all/platform/node_modules/karma-mocha/lib/mocha.js:4059
	uncaught@/home/southerd/devel/polymer/polymer-all/platform/node_modules/karma-mocha/lib/mocha.js:4089
	
Firefox 22.0.0 (Linux): Executed 17 of 17 (1 FAILED) (6.545 secs / NaN secs)
Chrome 28.0.1500 (Linux): Executed 17 of 17 (1 FAILED) (4.444 secs / NaN secs)
TOTAL: 2 FAILED, 32 SUCCESS
Warning: Task "karma:platform" failed. Use --force to continue.

Aborted due to warnings.
```