Fix 'Unexpected event error.'
Fix - Remove useless fire method.

stateChange event is fired automatically while the value of state attribute
is modified.  You don't have to fire it manually.
Fix - Remove useless 'play' event publish.
Loads IFrame API when it's necessary.
Make container attribute becomes more flexible.
Add mock class of YT.Player.
Use mock class and make each test being independent.
Add several minor fixes.

* Add _createContainer method so initializer can focus doing its job.
* Disable the _poll log because it's too annoying.
* Fix for JSLint.
Update README.md
Merge pull request #4 from josephj/master

Avoid to fire attribute "stateChange" event manually