fix(package): update envalid to version 6.0.2

Closes #69

Author: greenkeeper[bot]

package.json

@@ -4,7 +4,7 @@
   "dependencies": {
     "amqplib": "^0.5.0",
     "boom": "^5.2.0",
-    "envalid": "^5.0.0",
+    "envalid": "^6.0.2",
     "good": "^7.0.2",
     "good-console": "^7.0.0",
     "good-squeeze": "^5.0.0",