Laravel 5.4/5.5 support

[fgm]

• Implement the 5.5-new handle() vs fire() command method.
• Add the 5.5-new extra/laravel section in composer.json.
• Implement the provides() method on the service provider.
• Require the PSR7 message bridge to include Diactoros needed by RoutingServiceProvider.
• Require a few dependencies needed by the default Laravel project configuration.
• Might need to go into a separate branch in case it breaks Laravel 4 projects