Switch to Github Actions with auto binary release

[jpillora]

Plus, replace Godep/vendor with go mod

Edit: Just realised this doesn't do the docker release, is the docker image used often?

[ddollar]

Thanks! Will take a look at this after the new year once the holiday craziness dies down :)

[jpillora]

i updated jpillora/go-template from which this PR based

see that repo if interested