Upgrade dependencies to Laravel 5.6.39

composer.json

@@ -5,20 +5,22 @@
     "license": "MIT",
     "type": "project",
     "require": {
-        "php": ">=7.0.0",
+        "php": "^7.1.3",
         "backup-manager/laravel": "^1.3",
         "barryvdh/laravel-dompdf": "^0.8.0",
         "laracasts/flash": "~2",
-        "laravel/framework": "5.5.*",
+        "fideloper/proxy": "^4.0",
+        "laravel/framework": "5.6.*",
         "league/flysystem": "^1.0",
         "luthfi/formfield": "^0.2"
     },
     "require-dev": {
-        "laravel/browser-kit-testing": "^2.0",
-        "barryvdh/laravel-debugbar": "^2.0",
-        "fzaninotto/faker": "~1.4",
-        "mockery/mockery": "0.9.*",
-        "phpunit/phpunit": "~6.0"
+        "laravel/browser-kit-testing": "^4.0",
+        "barryvdh/laravel-debugbar": "^3.1",
+        "filp/whoops": "^2.0",
+        "fzaninotto/faker": "^1.4",
+        "mockery/mockery": "^1.0",
+        "phpunit/phpunit": "^7.0"
     },
     "autoload": {
         "classmap": [
@@ -55,5 +57,7 @@
         "preferred-install": "dist",
         "sort-packages": true,
         "optimize-autoloader": true
-    }
+    },
+    "minimum-stability": "dev",
+    "prefer-stable": true
 }