Non-Zero MessageID when QoS > 0 (#251)

* Non-Zero MessageId when QoS > 0

Aligned the MQTT 3.1.1 spec, http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718025

* Prolong waiting time (#252)

Travis CI sometimes is too slow, and is causing aedes broker not respond and fails the 'disconnect if a connect does not arrive in time' test

* Replace istanbul with nyc (#253)

* Replace istanbul with nyc

istanbul is not maintained anymore

* Update .gitignore

* Non-Zero MessageId when QoS > 0

Aligned the MQTT 3.1.1 spec, http://docs.oasis-open.org/mqtt/mqtt/v3.1.1/os/mqtt-v3.1.1-os.html#_Toc398718025

lib/qos-packet.js

@@ -11,7 +11,7 @@ function QoSPacket (original, client) {
   if (!original.messageId) {
     this.messageId = client._nextId
     if (client._nextId === 65535) {
-      client._nextId = 0
+      client._nextId = 1
     } else {
       client._nextId++
     }