artisan serve for Lumen projects

1. composer require mlntn/lumen-artisan-serve "~1"

2. Add the following line to the $commands array in app/Console/Kernel.php:

   \Mlntn\Console\Commands\Serve::class,

3. artisan serve

I didn't write most of this code. It comes straight from laravel/framework by @taylorotwell. I did have to tweak a few things to get it going for Lumen. Enjoy!