Docker image for goreleaser

[jadwahab]

Right now goreleaser has it's own built binary so we just copy it over into the docker image but then we have some duplication so we have 2 Dockerfiles. (one for local builds and one for releaser builds)

[roppa]

I took a look at goreleaser, looks like as we are using cgo its making it a little more complicated. We can either add a lot more lines of code to the gorelaser yml file, or keep the docker file as is. See https://goreleaser.com/cookbooks/cgo-and-crosscompiling/