Fix Error => Errorf
Fix Error => Errorf

This bugfix brought to you by `go vet`

w4ngyi/goji,dbmlabs/goji,vanackere/slim,Invacio/goji,yangou/goji,beni55/goji,vsco/goji,zenazn/goji,unixorn/goji,tchssk/goji,cognusion/goji