Base conversion (and alphabetizing imports)

Racpete can now translate numbers between bases! I also made things alphabetical because it was bothering me. The convert-base code is pretty ugly, I think, but I couldn't figure out a good idiomatic way to do it. Point me in the right direction and I can fix it :)
A note about testing in racket: I think for unit tests it tends to be more common to have the unit tests for a file be in a submodule of that file. Like how it is in derek.rkt although it wouldn't bother me if these tests live here