[chore] Bump superagent and supertest versions (#3186)

Author: darrachequesne

package.json

@@ -35,8 +35,8 @@
     "expect.js": "0.3.1",
     "mocha": "^3.5.3",
     "nyc": "^11.2.1",
-    "superagent": "1.6.1",
-    "supertest": "1.1.0"
+    "superagent": "^3.8.2",
+    "supertest": "^3.0.0"
   },
   "contributors": [
     {