package.json: Add packages that will be needed soon

Add "express" and "morgan" packages, which will be needed by
soon-to-be-introduced spec server and benchmark server.

See #442.

package.json

@@ -52,8 +52,10 @@
     "babelify": "7.3.0",
     "browserify": "13.1.0",
     "eslint": "2.13.1",
+    "express": "4.14.0",
     "http-server": "0.9.0",
     "jasmine-node": "1.14.5",
+    "morgan": "1.7.0",
     "uglify-js": "2.7.0"
   },
   "engines": {