Crash the app if does not find index.html, index.js or favico.ico

Created by: vnctaing

Hi,

I saw that issue(https://github.com/facebookincubator/create-react-app/issues/96) needed help, it had previously a PR that have been closed few weeks back. I don't know if someone is still working this. So I tried to solve the issue

How can I improve my PR ?

Thanks !