fix(package): update express to version 4.17.1

Closes #42

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
     "codemirror": "5.20.2",
     "cross-env": "^3.1.3",
     "css-loader": "0.25.0",
-    "express": "4.14.0",
+    "express": "4.17.1",
     "extract-text-webpack-plugin": "1.0.1",
     "findup": "0.1.5",
     "glob": "7.1.1",