fix(package): update superagent to version 4.0.0

Author: greenkeeper[bot]

Diff for: package.json

@@ -31,7 +31,7 @@
   "dependencies": {
     "lodash": "^4.17.4",
     "pelias-logger": "^1.2.1",
-    "superagent": "^3.5.2"
+    "superagent": "^4.0.0"
   },
   "pre-commit": [
     "lint",