Go 1.13 and up enforce import paths to be versioned if a project
contains a go.mod and has released v2 or up.
The current v2.x branches (and releases) do not yet have a go.mod,
and therefore are still allowed to be imported with a non-versioned
import path (go modules add a `+incompatible` annotation in that case).
However, now that this project has a `go.mod` file, incompatible
import paths will not be accepted by go modules, and attempting
to use code from this repository will fail.
This patch uses `v3` for the import-paths (not `v2`), because changing
import paths itself is a breaking change, which means that the
next release should increment the "major" version to comply with
SemVer (as go modules dictate).
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
