Issues 1882

Added a check to call opt_parser to print usage information if no argument is passed to chef-apply as requested in issue 1882.
You could put a more useful message than Exiting in the message (this gets piped out through Chef::Log.debug), although I realize we don't elsewhere.

I think we should exit 1 here instead of 0. Maybe you wanted to get the help output so you might consider this success, but I could imagine a case where something gets messed up and only chef-apply is run in a script and you don't capture that because it is exiting with success.