Fix L8 cached routes (#29)

* Fix L8 cached routes

This will fix the following error when using cached routes without the $namespace member in your RouteServiceProvider:

```
Argument 1 passed to CodeZero\LocalizedRoutes\UrlGenerator::__construct() must be an instance of Illuminate\Routing\RouteCollection, instance of Illuminate\Routing\CompiledRouteCollection given, called in /var/www/vendor/codezero/laravel-localized-routes/src/LocalizedRoutesServiceProvider.php on line 104
```

* Remove incompatible dependencies,
Remove tests for deprecated versions,

* Remove function type hint, check type manually,
Add back support & testing for L5.6+,

* Fix code standard

* Update condition

Author: bumbummen99

composer.json

@@ -26,7 +26,7 @@
         "illuminate/support": "^5.6|^6.0|^7.0|^8.0"
     },
     "require-dev": {
-        "mockery/mockery": "^1.3",
+        "mockery/mockery": "^1.0",
         "orchestra/testbench": "^3.6|^4.0|^5.0|^6.0",
         "phpunit/phpunit": "^7.0|^8.0|^9.0"
     },

src/UrlGenerator.php

@@ -18,8 +18,12 @@ class UrlGenerator extends BaseUrlGenerator
      * @param \Illuminate\Http\Request $request
      * @param string $assetRoot
      */
-    public function __construct(RouteCollection $routes, Request $request, $assetRoot = null)
+    public function __construct($routes, Request $request, $assetRoot = null)
     {
+        if (!$routes instanceof RouteCollection && !(class_exists('Illuminate\Routing\RouteCollectionInterface') && is_subclass_of($routes, 'Illuminate\Routing\RouteCollectionInterface'))) {
+            throw new \InvalidArgumentException('The $routes parameter has to be of type RouteCollection or RouteCollectionInterface for L6+.');
+        }
+        
         parent::__construct($routes, $request, $assetRoot);
     }