New forks fail to build because of missing dependencies

I think this is occurring because absolute import paths are being used when relative paths may be required, but this issue is pervasive, so I wanted to get some feedback before creating a pull request.

Should the import statements refer to e.g. toxiproxy/stream or just stream (I'm not fluent in Go), rather than github.com/Shopify/toxiproxy/stream? The current imports have the effect of directing Go to look for those packages in the vendor/ directory when a fork builds (see sample Travis log snippet below).

NB I did briefly look at the docs for the tools/godep project, but it appears to be deprecated.

An example is link.go:

package toxiproxy

import (
	"io"
	"github.com/Shopify/toxiproxy/stream"
	"github.com/Shopify/toxiproxy/toxics"
	"github.com/sirupsen/logrus"
)

This results in build errors on a fresh fork:

$ godep go build
link.go:6:2: cannot find package "github.com/Shopify/toxiproxy/stream" in any of:
	/home/travis/gopath/src/github.com/jimkleine/toxiproxy/vendor/github.com/Shopify/toxiproxy/stream (vendor tree)
	/home/travis/.gimme/versions/go1.9.7.linux.amd64/src/github.com/Shopify/toxiproxy/stream (from $GOROOT)
	/home/travis/gopath/src/github.com/jimkleine/toxiproxy/Godeps/_workspace/src/github.com/Shopify/toxiproxy/stream (from $GOPATH)
	/home/travis/gopath/src/github.com/Shopify/toxiproxy/stream
api.go:12:2: cannot find package "github.com/Shopify/toxiproxy/toxics" in any of:
	/home/travis/gopath/src/github.com/jimkleine/toxiproxy/vendor/github.com/Shopify/toxiproxy/toxics (vendor tree)
	/home/travis/.gimme/versions/go1.9.7.linux.amd64/src/github.com/Shopify/toxiproxy/toxics (from $GOROOT)
	/home/travis/gopath/src/github.com/jimkleine/toxiproxy/Godeps/_workspace/src/github.com/Shopify/toxiproxy/toxics (from $GOPATH)
	/home/travis/gopath/src/github.com/Shopify/toxiproxy/toxics
godep: go exit status 1
The command "godep go build" failed and exited with 1 during .

The equivalent Travis build log from the Shopify repo is:

$ godep go build
10.28s$ godep go test ./...
ok  	github.com/Shopify/toxiproxy	0.579s
?   	github.com/Shopify/toxiproxy/cli	[no test files]
?   	github.com/Shopify/toxiproxy/client	[no test files]
?   	github.com/Shopify/toxiproxy/cmd	[no test files]
ok  	github.com/Shopify/toxiproxy/stream	0.052s
ok  	github.com/Shopify/toxiproxy/testhelper	0.010s
ok  	github.com/Shopify/toxiproxy/testing	0.010s [no tests to run]
ok  	github.com/Shopify/toxiproxy/toxics	6.507s
The command "godep go test ./..." exited with 0.

Start with the imports in link.go and api.go, then run godep go build from a fresh fork to reproduce the missing-package errors. Compare the fork's vendor and Godeps paths with the successful Shopify Travis build. Done means a fresh fork builds and godep go test ./... completes successfully.