Laravel 5.7 support

[martijn94]

Hi,

Thanks for making this package publicly available.

Due to the requirement "illuminate/support": "5.6.*" the package does not install out of the box on Laravel 5.7.

I can confirm the package working perfectly fine on 5.7.

[HelgeSverre]

Created a PR
#24

[Naoray]

@HelgeSverre maybe u should fork the pkg and create and mantain ur own copy. Guess this pkg won't be mantained anymore

[peterjaap]

I made these changes (and more) in my own fork https://github.com/elgentos/laravel-harvest