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/httpdown/readme.md

@@ -1,41 +0,0 @@
-httpdown [![Build Status](https://secure.travis-ci.org/facebookgo/httpdown.png)](https://travis-ci.org/facebookgo/httpdown)
-========
-
-Documentation: https://godoc.org/github.com/facebookgo/httpdown
-
-Package httpdown provides a library that makes it easy to build a HTTP server
-that can be shutdown gracefully (that is, without dropping any connections).
-
-If you want graceful restart and not just graceful shutdown, look at the
-[grace](https://github.com/facebookgo/grace) package which uses this package
-underneath but also provides graceful restart.
-
-Usage
------
-
-Demo HTTP Server with graceful termination:
-https://github.com/facebookgo/httpdown/blob/master/httpdown_example/main.go
-
-1. Install the demo application
-
-        go get github.com/facebookgo/httpdown/httpdown_example
-
-1. Start it in the first terminal
-
-        httpdown_example
-
-   This will output something like:
-
-        2014/11/18 21:57:50 serving on http://127.0.0.1:8080/ with pid 17
-
-1. In a second terminal start a slow HTTP request
-
-        curl 'http://localhost:8080/?duration=20s'
-
-1. In a third terminal trigger a graceful shutdown (using the pid from your output):
-
-        kill -TERM 17
-
-This will demonstrate that the slow request was served before the server was
-shutdown. You could also have used `Ctrl-C` instead of `kill` as the example
-application triggers graceful shutdown on TERM or INT signals.