fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/npm:debug:20170905
- https://snyk.io/vuln/npm:fresh:20170908
- https://snyk.io/vuln/npm:mime:20170907
- https://snyk.io/vuln/npm:ms:20170412

package.json

@@ -14,16 +14,16 @@
     "server"
   ],
   "dependencies": {
-    "debug": "~2.2.0",
+    "debug": "~2.6.9",
     "depd": "~1.1.0",
     "destroy": "~1.0.4",
     "encodeurl": "~1.0.1",
     "escape-html": "~1.0.3",
     "etag": "~1.7.0",
-    "fresh": "0.3.0",
+    "fresh": "0.5.2",
     "http-errors": "~1.5.0",
-    "mime": "1.3.4",
-    "ms": "0.7.1",
+    "mime": "1.4.1",
+    "ms": "2.0.0",
     "on-finished": "~2.3.0",
     "range-parser": "~1.2.0",
     "statuses": "~1.3.0"