[nit] Fix "go get" path for golint
[nit] Fix "go get" path for golint

resolve the following error.

> can't load package: package github.com/golang/lint/golint: code in directory
> /path/to/gopath/src/github.com/golang/lint/golint expects import "golang.org/x/lint/golint"

mackerelio/mkr,mackerelio/mkr