wip: some more drastic refactoring

testingt.go

@@ -0,0 +1,10 @@
+package golden
+
+// TestingT is a interface describing a sub-set of methods of *testing.T which
+// golden uses.
+type TestingT interface {
+	Fatalf(format string, args ...interface{})
+	Helper()
+	Logf(format string, args ...interface{})
+	Name() string
+}