JMS #25: Added support for help flags

## Help Flags Support
cli.go now supports help flags "-h/--help" for showing help. I also exposed a couple new methods to the Public interface for showing help and version, `ShowVersion`, `ShowAppHelp`, and `ShowCommandHelp`.

This PR is in reference to issue #25 
@SJD I am going to keep this PR up for the better part of today in case you want to eyeball it, after some time I will land it.

closes #25