command line option documentation

[dgutman]

Since in most cases people will want to "run" deid, I think it would be useful to specify the -o output flag if you run ./imagedephi with no options or with --help. I had to do then do ./imagedephi run --help

Probably useful to have this output most common use case in the initial -v or if you just run ./imagedephi.

[manthey]

If there is a way in click to add command examples when no subcommand is given, that would help.