Updating go depencancies. Switching to go1.6 vendoring (#2949)

vendor/github.com/pborman/uuid/CONTRIBUTING.md

@@ -0,0 +1,10 @@
+# How to contribute
+
+We definitely welcome patches and contribution to this project!
+
+### Legal requirements
+
+In order to protect both you and ourselves, you will need to sign the
+[Contributor License Agreement](https://cla.developers.google.com/clas).
+
+You may have already signed it for other Google projects.