Added additional grammar setting.

I added another setting for a comma delimited list pertaining to additional grammars.
![image](https://cloud.githubusercontent.com/assets/4511972/3923397/1079ce8e-23d3-11e4-94cc-ace53c86a8df.png)

just `grammar` or `supportedGrammars` would be better, since this includes both the default and any additional included by the user