add laravel 6.0 support

[Tamrael]

let's add laravel 6.0 support. str_ and arr_ helpers got dropped so let's use Arr:: and Str:: instead

[roblesterjr04]

I'm closing this because I have already made the necessary changes. You can work with the branch support60 if you want to do your own tests. I will be creating a release this week - all tests seem to pass.