Added basic support for warnings.

Added support for warnings.
This uses a blue "squiggly" to show where warnings currently are.

There is work that may be needed to be done in the omnisharp server to show the positions of warnings a bit better.

Preview : 

![image](https://cloud.githubusercontent.com/assets/237469/5071583/16c3afd0-6e6a-11e4-8cf9-289ab48f067e.png)


_Note : Omnisharp will only report warnings if there are 0 errors in that document_