Vendor gotestyourself

and remove testify and spew

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

vendor/github.com/stretchr/testify/assert/forward_assertions.go

@@ -1,16 +0,0 @@
-package assert
-
-// Assertions provides assertion methods around the
-// TestingT interface.
-type Assertions struct {
-	t TestingT
-}
-
-// New makes a new Assertions object for the specified TestingT.
-func New(t TestingT) *Assertions {
-	return &Assertions{
-		t: t,
-	}
-}
-
-//go:generate go run ../_codegen/main.go -output-package=assert -template=assertion_forward.go.tmpl