Autocompletion and man pages

[BrianHicks]

Cobra will automatically generate man pages and bash autocompletion for us. We should add that. I like Cockroach's approach:

$ cockroach gen -h
Generate manpages, example shell settings, example databases, etc.

Usage:
  cockroach gen [command] [flags]
  cockroach gen [command]

Available Commands:
  man          generate man pages for CockroachDB
  autocomplete generate bash autocompletion script for CockroachDB