Add dependency of `go fmt` in `Makefile` (#553)
Add dependency of `go fmt` in `Makefile` (#553)

This fix adds the dependency of `go fmt` in `Makefile`
so that any new check in will have to properly fmt the source code
with `gofmt -s -w`.
yongtang/coredns,johnbelamaric/coredns,varyoo/coredns,ii/coredns,jremond/coredns,miekg/coredns,chrisohaver/coredns,miekg/coredns,johnbelamaric/coredns,jremond/coredns,coredns/coredns,ii/coredns