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/couchbase/vellum/CONTRIBUTING.md

@@ -1,16 +0,0 @@
-# Contributing to Vellum
-
-We look forward to your contributions, but ask that you first review these guidelines.
-
-### Sign the CLA
-
-As Vellum is a Couchbase project we require contributors accept the [Couchbase Contributor License Agreement](http://review.couchbase.org/static/individual_agreement.html). To sign this agreement log into the Couchbase [code review tool](http://review.couchbase.org/). The Vellum project does not use this code review tool but it is still used to track acceptance of the contributor license agreements.
-
-### Submitting a Pull Request
-
-All types of contributions are welcome, but please keep the following in mind:
-
-- If you're planning a large change, you should really discuss it in a github issue first. This helps avoid duplicate effort and spending time on something that may not be merged.
-- Existing tests should continue to pass, new tests for the contribution are nice to have.
-- All code should have gone through `go fmt`
-- All code should pass `go vet`