Remove unneeded code

[moozzyk]

Looks like we assign the ShowHelp action to app.OnExecute but then a few lines below we overwrite it with the application logic. The first assignment is always overwritten so it's not needed.
As a sidenote - returning 2 does not seem to be correct - I believe we should return 0 for --help.

Related to #14

[BrennanConroy]

cbc201a