message: Add querystring dep. already used by things like url_utils.js.
diff: "matrix-js-sdk": "0.8.5",
  "optimist": "^0.6.1",
  "prop-types": "^15.5.8",
  + "querystring": "^0.2.0",
  "react": "^15.4.0",
  "react-addons-css-transition-group": "15.3.2",
  "react-dom": "^15.4.0",
  