Added in hook in main controller for displaying server connection errors

There were some deletions in the `/dist` directory. I can update the request to fix. 

1. Updated `src/scripts/controllers/main.js` to use a returned promise from the navigator module to alert us of any connection issues to a server.
2. Updated `src/scripts/siren/module.js` to have the `deferred` variable reject on an error from a `GET` request.