Added command aliases

[raffis]

Clean new pr for #14. Sorry for the delay!

Missing command aliases as a feature.

For example such a thing is now possible:

      .subCommand<CreateOptions, CreateArgs>('access-roles [name]')
      .alias('ar')
      .description('Create new access role')
      .action(this.execute.bind(this));

It's possible now to execute the commands callback with access-role or ar.

[raffis]

friendly reminder