Update traefik dependencies (docker/docker and related) (#1823)

Update traefik dependencies (docker/docker and related)

- Update dependencies
- Fix compilation problems
- Remove vdemeester/docker-events (in docker api now)
- Remove `integration/vendor`
- Use `testImport`
- update some deps.
- regenerate the lock from scratch (after a `glide cc`)

vendor/github.com/google/go-github/github/issues_labels.go

@@ -19,7 +19,7 @@ type Label struct {
 }
 
 func (l Label) String() string {
-	return fmt.Sprint(*l.Name)
+	return Stringify(l)
 }
 
 // ListLabels lists all labels for a repository.