Add godep usage information

Author: tgerring

README.md

@@ -92,6 +92,8 @@ are ignored (use gofmt!). If you send pull requests make absolute sure that you
 commit on the `develop` branch and that you do not merge to master.
 Commits that are directly based on master are simply ignored.
 
+For dependency management, we use [godep](https://github.com/tools/godep). After installing with `go get github.com/tools/godep`, run `godep restore` to ensure that changes to other repositories do not break the build. To update a dependency version (for example, to include a new upstream fix), run `go get -u <foo/bar>` then `godep update <foo/...>`. To track a new dependency, add it to the project as normal than run `godep save ./...`. Changes to the Godeps folder should be manually verified then commited.
+
 To make life easier try [git flow](http://nvie.com/posts/a-successful-git-branching-model/) it sets
 this all up and streamlines your work flow.