getForeignKey => getForeignKeyName (#53)

Fixing for laravel 5.8:
#50 #52

Author: Yahav

src/RelationFinder.php

@@ -80,7 +80,7 @@ protected function getRelationshipFromMethodAndModel(ReflectionMethod $method, s
 
                 if ($return instanceof BelongsTo) {
                     $foreignKey = $this->getParentKey($return->getQualifiedOwnerKeyName());
-                    $localKey = $return->getForeignKey();
+                    $localKey = $return->getForeignKeyName();
                 }
 
                 return [
@@ -97,4 +97,4 @@ protected function getRelationshipFromMethodAndModel(ReflectionMethod $method, s
         return null;
     }
 
-}
+}