chore(package): update should to version 13.1.1

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
   "devDependencies": {
     "mocha": "^3.2.0",
     "nyc": "^11.0.2",
-    "should": "^13.0.1",
+    "should": "^13.1.1",
     "standard": "^10.0.2"
   },
   "dependencies": {