Bump queue-worker and NATS

NATS moved its primary library to: github.com/nats-io/stan.go

This commit synchronises the library in the gateway to match the
queue worker.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

gateway/vendor/github.com/nats-io/jwt/header.go

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2018-2019 The NATS Authors
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package jwt
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+const (
+	// Version is semantic version.
+	Version = "0.3.2"
+
+	// TokenTypeJwt is the JWT token type supported JWT tokens
+	// encoded and decoded by this library
+	TokenTypeJwt = "jwt"
+
+	// AlgorithmNkey is the algorithm supported by JWT tokens
+	// encoded and decoded by this library
+	AlgorithmNkey = "ed25519"
+)
+
+// Header is a JWT Jose Header
+type Header struct {
+	Type      string `json:"typ"`
+	Algorithm string `json:"alg"`
+}
+
+// Parses a header JWT token
+func parseHeaders(s string) (*Header, error) {
+	h, err := decodeString(s)
+	if err != nil {
+		return nil, err
+	}
+	header := Header{}
+	if err := json.Unmarshal(h, &header); err != nil {
+		return nil, err
+	}
+
+	if err := header.Valid(); err != nil {
+		return nil, err
+	}
+	return &header, nil
+}
+
+// Valid validates the Header. It returns nil if the Header is
+// a JWT header, and the algorithm used is the NKEY algorithm.
+func (h *Header) Valid() error {
+	if TokenTypeJwt != strings.ToLower(h.Type) {
+		return fmt.Errorf("not supported type %q", h.Type)
+	}
+
+	if AlgorithmNkey != strings.ToLower(h.Algorithm) {
+		return fmt.Errorf("unexpected %q algorithm", h.Algorithm)
+	}
+	return nil
+}