This commit modernizes the repository organization a bit.

In short, this,

- Upgrades to Go 1.11.
- Uses Go modules instead of Glide.
- Drops errcheck, which we rarely use in our codebase internally.
- Uses `./...` to run build, tests, etc. since that does not have to
  account for vendor anymore.
- Drops `-installsuffix cgo` from the production build. This was a
  workaround for pre-1.10 versions of Go. See
  https://github.com/golang/go/issues/9344#issuecomment-69944514.
- Uses a tools.go as recommended in [go-modules-by-example/tools][1] to
  pin to tool dependencies.
- Uses `go run` instead of `go install`ing tools globally.

[1]: https://github.com/go-modules-by-example/index/tree/master/010_tools

Tested locally with `make docker-launch`.