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/lib/pq/CONTRIBUTING.md

@@ -1,29 +0,0 @@
-## Contributing to pq
-
-`pq` has a backlog of pull requests, but contributions are still very
-much welcome. You can help with patch review, submitting bug reports,
-or adding new functionality. There is no formal style guide, but
-please conform to the style of existing code and general Go formatting
-conventions when submitting patches.
-
-### Patch review
-
-Help review existing open pull requests by commenting on the code or
-proposed functionality.
-
-### Bug reports
-
-We appreciate any bug reports, but especially ones with self-contained
-(doesn't depend on code outside of pq), minimal (can't be simplified
-further) test cases. It's especially helpful if you can submit a pull
-request with just the failing test case (you'll probably want to
-pattern it after the tests in
-[conn_test.go](https://github.com/lib/pq/blob/master/conn_test.go).
-
-### New functionality
-
-There are a number of pending patches for new functionality, so
-additional feature patches will take a while to merge. Still, patches
-are generally reviewed based on usefulness and complexity in addition
-to time-in-queue, so if you have a knockout idea, take a shot. Feel
-free to open an issue discussion your proposed patch beforehand.