fix(package): update express-session to version 1.17.1

Closes #54

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
     "compression": "1.7.1",
     "cookie-parser": "1.4.3",
     "expect.js": "0.3.1",
-    "express-session": "1.15.6",
+    "express-session": "1.17.1",
     "glob": "7.1.1",
     "lodash": "^4.17.4",
     "mv": "2.1.1",