Update upgrad guide.

upgrade.md

@@ -2,7 +2,7 @@
 
 ## Upgrading From 4.0 to 4.1
 
-- Update `composer.json` to require `"laravel/framework": "4.1.*"` 
+- Update `composer.json` to require `"laravel/framework": "4.1.*"`
 - `composer update`.
 - Replace `public/index.php`, `artisan.php`.
 - Add new `expire_on_close` option to `session` configuration file.
@@ -17,3 +17,4 @@
 - If you are overriding `missingMethod` in your controllers, add $method as the first parameter.
 - Password reminder system tweaked for greater developer freedom. Inspect stub controller by running `auth:reminders-controller` Artisan command.
 - Update `reminders.php` language file.
+- If you are using http hosts to set the $env variable in bootstrap/start.php, these should be changed to machine names (as returned by PHP's gethostname() function).