added composer.lock to repository

First commit: After running "composer install" the file composer.lock is generated. I added this file to the repository. It's the standard way of doing things to have it committed.

Second commit: I also setup the use of the standard cdn for bootstrap in the twitter example for getting bootstrap.css. The previous url "http://jasny.github.com/bootstrap/assets/css/bootstrap.css" was not valid. Better to use the std CDN.