Auto merge of #289 - kbknapp:issue-277, r=Vinatorul
Auto merge of #289 - kbknapp:issue-277, r=Vinatorul

fix(Help Message): required args no longer double list in usage

Closes #277

cstorey/clap-rs,clap-rs/clap,sru/clap-rs,clap-rs/clap,kbknapp/clap-rs,sru/clap-rs,Vinatorul/clap-rs,cstorey/clap-rs,sru/clap-rs,Vinatorul/clap-rs,Vinatorul/clap-rs,cstorey/clap-rs,kbknapp/clap-rs,clap-rs/clap