Closes #44: Adds VisualBasic Support

Tested by uploading a sample project (https://github.com/cwh05/IDBA) to SourceBrowser.Site and by feeding the same project into SourceBrowser.Samples

The CS/VB distintion is done on a per-document basis, so mixed C# and VB solutions should work, although I haven't tested a solution like this. If anyone knows of a solution like this (but smaller than Roslyn), please let me know