sg: use github.com/gomodule/redigo
Created by: keegancsmith
go get gives us this helpful warning:
go: module github.com/garyburd/redigo is deprecated: Use github.com/gomodule/redigo instead.
go: warning: github.com/gomodule/[email protected]+incompatible: retracted by module author: Old development version not maintained or published.
Note gomodule/redigo
is already what we use in the rest of the codebase.