added more information on running composer update when upgrading to 4.1

I had a different outcome when upgrading on a different server (shared hosting). I thought to share how I was able to circumvent that issue. Apparently, `composer update --no-scripts` doesn't always work. Though, running `composer update --no-scripts` did the trick on my local server at home.

Ravi.
This would be better:

Once you have completed the changes above, you can run the `composer update` function to update your core application files! If you receive class load errors, try running the `update` command with the `--no-scripts` option enabled like so: `composer update --no-scripts` (On Linux, you may have to run `sudo composer update` if you are getting Permission Denied errors). If you are having issues loading Controllers after running `composer update --no-scripts`, then edit app/config/app.php, changing `'Controller' => 'Illuminate\Routing\Controllers\Controller'` to `'Controller' => 'Illuminate\Routing\Controller'`.