Removing dependency on jwt

Signed-off-by: Matthias Hanel <mh@synadia.com>

go.mod

@@ -3,7 +3,7 @@ module github.com/nats-io/nats.go
 go 1.14
 
 require (
-	github.com/golang/protobuf v1.4.0
+	github.com/golang/protobuf v1.4.2
 	github.com/nats-io/nats-server/v2 v2.1.7
 	github.com/nats-io/nkeys v0.2.0
 	github.com/nats-io/nuid v1.0.1

go.sum

@@ -2,8 +2,9 @@ github.com/golang/protobuf v1.4.0-rc.1/go.mod h1:ceaxUfeHdC40wWswd/P6IGgMaK3YpKi
 github.com/golang/protobuf v1.4.0-rc.1.0.20200221234624-67d41d38c208/go.mod h1:xKAWHe0F5eneWXFV3EuXVDTCmh+JuBKY0li0aMyXATA=
 github.com/golang/protobuf v1.4.0-rc.2/go.mod h1:LlEzMj4AhA7rCAGe4KMBDvJI+AwstrUpVNzEA03Pprs=
 github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:WU3c8KckQ9AFe+yFwt9sWVRKCVIyN9cPHBJSNnbL67w=
-github.com/golang/protobuf v1.4.0 h1:oOuy+ugB+P/kBdUnG5QaMXSIyJ1q38wWSojYCb3z5VQ=
 github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
+github.com/golang/protobuf v1.4.2 h1:+Z5KGCizgyZCbGh1KZqA0fcLLkwbsjIzS4aV2v7wJX0=
+github.com/golang/protobuf v1.4.2/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw735rRwI=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.4.0 h1:xsAVV57WRhGj6kEIi8ReJzQlHHqcBYCElAvkovg3B/4=

nats_test.go

@@ -1436,13 +1436,6 @@ func TestUserCredentialsChainedFile(t *testing.T) {
 	nc.Close()
 }
 
-func createNewUserKeys() (string, []byte) {
-	kp, _ := nkeys.CreateUser()
-	pub, _ := kp.PublicKey()
-	priv, _ := kp.Seed()
-	return pub, priv
-}
-
 func TestExpiredUserCredentials(t *testing.T) {
 	// The goal of this test was to check how a client with an expiring JWT
 	// behaves. It should receive an async -ERR indicating that the auth