add 'sudo' to docker commands in release script

overridable with SUDO env var

bin/release

@@ -2,6 +2,7 @@
 
 set -e
 
+SUDO=sudo
 PWD=`pwd`
 GITHUB_USER=zettio
 DOCKERHUB_USER=zettio
@@ -123,9 +124,9 @@ publish() {
 
     for IMAGE in weave weavedns weavetools ; do
         echo == Tagging $DOCKERHUB_USER/$IMAGE as $VERSION
-        docker tag  $DOCKERHUB_USER/$IMAGE $DOCKERHUB_USER/$IMAGE:$VERSION
-        docker push $DOCKERHUB_USER/$IMAGE:$VERSION
-        docker push $DOCKERHUB_USER/$IMAGE:latest
+        $SUDO docker tag  $DOCKERHUB_USER/$IMAGE $DOCKERHUB_USER/$IMAGE:$VERSION
+        $SUDO docker push $DOCKERHUB_USER/$IMAGE:$VERSION
+        $SUDO docker push $DOCKERHUB_USER/$IMAGE:latest
         echo "** Pushed $DOCKERHUB_USER/$IMAGE:$VERSION to docker hub"
     done