Release Workflow Updates

[alexbhr]

Dear @hiyosi,

we use the hawk library internally at work for a few different services, and I wanted to start by thanking you on behalf of our whole dev team for writing hawk.

As part of ensuring the long term maintainability of various project dependencies, we decided to submit a set of Github Actions workflows to hawk that test the lib on various platforms and supported versions of Golang.

Some points about this PR:

• It runs go vet before go test to ensure sane syntax
• It maintains goveralls support across the matrix build of os/golang versions
• It creates a go.mod file for modern dependency management
• It introduces a Goreleaser trigger when new tags are pushed, which create a Github release along with a decent changelog of what changes
• It deprecates Travis by removing the .travis.yml file

If you decide to merge this, please pull the code locally and do a git tag v1.0.0 && git push origin master --tags to trigger the Goreleaser action.

Thanks again, and greetings to Japan from all of us out here!

[hiyosi]

@alexbhr
Thank you so much for your contribution!
I'll review this soon.

[hiyosi]

I'd like to thank you again.
I've created tag=v1.0.0.