Migrate to dep (#3972)

* Update makefile to use dep

* Migrate to dep

* Fix some deps

* Try to find a better version for golang.org/x/net

* Try to find a better version for golang.org/x/oauth2

vendor/github.com/facebookgo/stats/readme.md

@@ -1,4 +0,0 @@
-stats [![Build Status](https://secure.travis-ci.org/facebookgo/stats.png)](https://travis-ci.org/facebookgo/stats)
-=====
-
-Documentation: https://godoc.org/github.com/facebookgo/stats