added a 1 minute timeout to require.js.

Closes #604.

Turns out that require.js doesn't/can't cancel requests for scripts (since they are just `<script>` tags) but simply stops waiting for them to load so that the app can somehow react when things are broken. Since Kibana doesn't have any sort of backup plan in place for retrying on load failure, extending the timeout to 1 minute shouldn't have any negative side-effects.