Vendor gotestyourself

and remove testify and spew

Signed-off-by: Daniel Nephin <dnephin@gmail.com>

vendor/github.com/stretchr/testify/require/requirements.go

@@ -1,9 +0,0 @@
-package require
-
-// TestingT is an interface wrapper around *testing.T
-type TestingT interface {
-	Errorf(format string, args ...interface{})
-	FailNow()
-}
-
-//go:generate go run ../_codegen/main.go -output-package=require -template=require.go.tmpl