Basic CBN auto-complete with classes and declared variables

This PR includes autocompletion on (1) class names and (2) declared variables:

![image](https://cloud.githubusercontent.com/assets/5710686/4353938/28ff5d82-4239-11e4-9676-285458bb280b.png)
 
![image](https://cloud.githubusercontent.com/assets/5710686/4353954/6ed2657a-4239-11e4-9a7b-f026a83e21f1.png)