Remove dependency on compromised flatmap-stream package.

We use npm-run-all to build css before running the app in development mode. The version we were using depends, through ps-tree, on the event-stream package which has been compromised.

- indexzero/ps-tree#34
- dominictarr/event-stream#116
- dominictarr/event-stream#115

Upgrading to the latest npm-run-all fixes this issue.

package.json

@@ -19,7 +19,7 @@
     "immutable": "^3.8.2",
     "jquery": "^3.2.1",
     "node-sass-chokidar": "0.0.3",
-    "npm-run-all": "^4.1.2",
+    "npm-run-all": "^4.1.5",
     "popper.js": "^1.12.9",
     "qs": "^6.5.1",
     "react": "^16.2.0",