Fix a bug where the filter was returned but the callback was expected

Author: carlosV2

src/Funnel.php

@@ -188,6 +188,6 @@ public static function __callStatic($name, array $arguments)
         $filter = strtolower($matches[1]);
         self::assertFilterExists($filter);
 
-        return self::$filters[$filter];
+        return call_user_func_array(self::$filters[$filter], $arguments);
     }
 }

tests/FunnelTest.php

@@ -200,6 +200,7 @@ public function itReturnsTheTestingFilter()
         $filter = new TestingFilter();
         Funnel::addFilter($filter);
 
-        $this->assertEquals($filter->getFilter(), Funnel::testingFilter());
+        $callable = $filter->getFilter();
+        $this->assertEquals($callable('test'), Funnel::testingFilter('test'));
     }
 }