Fixed Credit Removal and Added Consistency

Removing credits was completely dysfunctional because it was confusing the amount arg(args[1]) for the player arg(args[2]). This was easy to fix. Color codes are now slightly more consistent(+/- errors being red). Also, any negative number will be rejected when adding/subtracting credits(as opposed to only rejecting -1 before, which led me to believe that you didn't want it to allow negative input), and the resulting message("not a positive #") is now more clear as to what the problem is(before it was "not a #").