chore(package): remove joi package dev dependency

Author: Hans Kristian Flaatten

package.json

@@ -47,7 +47,6 @@
     "express": "^4.13.4",
     "greenkeeper-postpublish": "^1.0.0",
     "istanbul": "^0.4.3",
-    "joi": "^9.0.0",
     "mocha": "^2.5.3",
     "mongodb": "^2.1.18",
     "nsp": "^2.4.0",