Clojurians Log v2

Sorry for all the pushes on the '*1, *2, *3' PR, @mfikes. I sort of made a meal of it with my original solution. I wouldn't have bothered rewriting the if-not form at the end of planck.repl/execute-source if I'd started with the solution of putting the check in planck.repl/process-1-2-3 but now that it's refactored (albeit, first with cond and now with case), it seems a little clearer compared to the original and so I've left it refactored.