Fix the broken tests for older laravel versions (#63)

* Sort the models to get the same results for laravel 5.6 as for the newer versions

* Make the relations backward compatible with < laravel 5.8

Author: daniel-werner

src/ModelFinder.php

@@ -40,7 +40,7 @@ public function getModelsInDirectory(string $directory): Collection
             return !empty($className)
                 && is_subclass_of($className, EloquentModel::class)
                 && ! (new ReflectionClass($className))->isAbstract();
-        })->diff($ignoreModels);
+        })->diff($ignoreModels)->sort();
     }
 
     protected function getFullyQualifiedClassNameFromFile(string $path): string

src/RelationFinder.php

@@ -80,7 +80,7 @@ protected function getRelationshipFromMethodAndModel(ReflectionMethod $method, s
 
                 if ($return instanceof BelongsTo) {
                     $foreignKey = $this->getParentKey($return->getQualifiedOwnerKeyName());
-                    $localKey = $return->getForeignKeyName();
+                    $localKey = method_exists($return, 'getForeignKeyName') ? $return->getForeignKeyName() : $return->getForeignKey();
                 }
 
                 return [