Visual Basic support

This pull request adds the Visual Basic support implemented by @AdamSpeight2008. Fixes #6.
Do we need `FullName` in VB? The below one seems to compile successfully:

```vb
Module Module1

    Sub Main()
    End Sub

    Sub Foo(foo As String)
        If foo Is Nothing Then Throw New ArgumentNullException("foo")
    End Sub

End Module
```