Parser interpreter

Adding two recipes, one to show off core.match via a S-expression parser, and the second to repurpose that parser as an interpreter for a simple language I called "Limited Clojure" or "LC" *wink* *wink*

I'm open to mechanical and stylistic suggestions for both recipes, but I'm particularly worried about the discussion in the interpreter recipe. I feel all the topics presented are necessary to understand the semantics of the interpreter, but it still feels like kind of heady stuff for the recipe format. 

I was also thinking about adding a section at the end that showed how LC could be more different from Clojure by adding a "change!" operator that works like Scheme's "set!" (since Clojure already has a set! with a different semantics). Again, I felt like the discussion was getting big anyway, so I've left it off for now.