go.mod for v0.1.1

[millergarym]

Please create a go.mod tagged v0.1.x release.

Simple as

go mod init  github.com/envoyproxy/protoc-gen-validate
rm Gopkg*
git add -u
git commit -m "go.mod"
git tag -a -m "go.mod" v0.1.1
git push --follow-tags

I'd create a PR, but can't PR against a tag only a branch :-(