mqtt: Allow any 1.x version > 1.4

Fixes #9

Author: jonnor

package.json

@@ -30,7 +30,7 @@
     "grunt-mocha-test": "^0.12.2",
     "grunt-shell-spawn": "^0.3.1",
     "mocha": "~1.21.0",
-    "mqtt": "1.4.x"
+    "mqtt": "^1.4.0"
   },
   "keywords": [],
   "bin": {