Clojurians Log v2

Exercism v3 is set to launch April 1st (which also happens to be my birthday!), so I'm working hard to get the Clojure track ready. It's been pretty much just me maintaining it, which has been a challenge both due to my non-expert status, and lack of code review. The current task at hand involves defining prerequisite concepts for each of the exercises (76 of them!) so that they can be presented in sensible learning paths. Any input here would be much appreciated, because I'm not familiar with all of the exercises, nor am I the best person to discern all the various ways they can be solved. This is the relevant PR: https://github.com/exercism/clojure/pull/330