Added a concatenateArgs method, so that we can easily concactenate
arrays that get returned from open-ended commands. E.g. /warn player
reason returns "player" and a bunch of arguments for each word in
"reason". Now we can just give the array to concatenateArgs() and it
will make us a nice array containing just two arguments.

next up: test method to make sure this works 100% correctly, and
implementation in the actual punishment class.