would like the usage exit status to be configurable

[trentm]

Currently node-cmdln's exitStatus for usage errors (OptionError, UsageError, NoCommandError) is 1. illumos tends to use 2, other tools on Mac seem to be 1, sendmail originating "sysexits.h" EX_USAGE=64, bash uses 2 for usage errors. IOW, there isn't a super strong general pattern that node-cmdln could proscribe. Really the app (the user of node-cmdln) should be able to set this.