mqtt: Require 2.x

Author: jonnor

package.json

@@ -30,7 +30,7 @@
     "coffee-script": "^1.10.0",
     "mocha": "^3.2.0",
     "amqplib": "^0.5.1",
-    "mqtt": "~2.13.0",
+    "mqtt": "^2.13.0",
     "msgflo": "^0.10.19"
   }
 }