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/docker/docker/client/secret_remove.go

@@ -0,0 +1,10 @@
+package client
+
+import "golang.org/x/net/context"
+
+// SecretRemove removes a Secret.
+func (cli *Client) SecretRemove(ctx context.Context, id string) error {
+	resp, err := cli.delete(ctx, "/secrets/"+id, nil, nil)
+	ensureReaderClosed(resp)
+	return err
+}