New set class

[Stephan Diehl]

Michiel wrote:
> I have written a new class to represent sets, with several useful
> features. Uploaded for your review and free use. I don't know much about
> open source and licensing, but I request that if you use the class, that
> you keep my name in the author section of the documentation.
> 
> http://files.michiel.eu/set.d
> 
> Tell me what you think.
> 

excelent. I somewhat missed some subset operations. If it were up to me, 
I'd use the opCmp operator for this (just like they do in python).