concise Clojure primer?

[light-matters]

Added this from a PR request.

@holyjak said:

< Not sure a random scientist knows by now what a Clojure list is, and what "unevaluated" means in this context.

< Perhaps we should write a conscise Clojure Primer and then link to it from places like this one? We could perhaps start with these three slides and add a section on symbols and evaluated vs unevaluated code...