Fix for #69 NSpec and VB.NET

Had a go at fixing #69:

Added a NSpecSpecsVB project containing a small number of tests of NSpec being called from VB.NET where anonymous lambdas are named like 'Void_Lambda$__1'.
Added TheExampleCount to when_running_specs.cs to support the VB specs that show the problem.
Fixed the problem with suggestion in DomainExtensions.cs, filtering out method names contain a '<' or a '$'.
Added running of NSpecSpecsVB to Rakefile.

Happy to take feedback and revise if needed.

Thanks for your help so far.