`lein run` prints every task regardless of input

[cstby]

Tested on a new template. I expected that it would only print the answer for the problem I specify (e.g. d01.p2). In my own solutions this year, I fixed this problem by removing println from inside the case body. Instead, I wrapped the entire case call in printlin. That resulted in the expected behavior, but I don't know if that's the ideal solution.

[mhanberg]

PR's are welcome!