Bump redis for CVE

Author: NickCraver

package.json

@@ -49,7 +49,7 @@
     "debug": "^2.6.1",
     "mocha": "^2.5.3",
     "pug": "^2.0.0-beta2",
-    "redis": "^2.6.1",
+    "redis": "^3.1.1",
     "request": "^2.73.0",
     "vision": "^4.1.0"
   }