add vendor & update README.md

vendor/github.com/gorilla/securecookie/fuzz.go

@@ -0,0 +1,25 @@
+// +build gofuzz
+
+package securecookie
+
+var hashKey = []byte("very-secret12345")
+var blockKey = []byte("a-lot-secret1234")
+var s = New(hashKey, blockKey)
+
+type Cookie struct {
+	B bool
+	I int
+	S string
+}
+
+func Fuzz(data []byte) int {
+	datas := string(data)
+	var c Cookie
+	if err := s.Decode("fuzz", datas, &c); err != nil {
+		return 0
+	}
+	if _, err := s.Encode("fuzz", c); err != nil {
+		panic(err)
+	}
+	return 1
+}