Updated compatibility to Laravel 5.6

[hfalucas]

The upgrade guide for L5.6 doesn't seem to introduce any breaking changes.

[hmazter]

This fork/branch seems to work fine with a 5.6 project

[bissolli]

Hey @hipsterjazzbo , any plans to accept it?

[hfalucas]

While this PR is not merged and you want to update your Laravel version:

1. Change the package version:
   "hipsterjazzbo/landlord": "dev-master"

2. Add this block to your composer.json file:

"repositories": [
    {
        "type": "vcs",
        "url":  "git@github.com:hfalucas/Landlord.git"
    }
]

[mbardelmeijer]

@hipsterjazzbo ping 🙈

[bissolli]

No news on accepting it? =/

[iNaD]

Tried to reach him on Twitter some time ago (he asked for someone taking over Landlord), but did not receive any answer yet.