Add logic to automatically select the best caching strategy

Based on the number of unique shared strings as well as the available memory amount,
one strategy will be chosen over the other.
The algorithm is based on empirical data and super safe so it may need to be tuned.

tests/Spout/ReflectionHelper.php

@@ -89,4 +89,27 @@ class ReflectionHelper
 
         return $value;
     }
+
+    /**
+     * Invoke a the given public or protected method on the given object.
+     *
+     * @param object $object
+     * @param string $methodName
+     * @param *mixed|null $params
+     *
+     * @return mixed|null
+     */
+    public static function callMethodOnObject($object, $methodName)
+    {
+        $params = func_get_args();
+        array_shift($params); // object
+        array_shift($params); // methodName
+
+        $className = get_class($object);
+        $class = new ReflectionClass($className);
+        $method = $class->getMethod($methodName);
+        $method->setAccessible(true);
+
+        return $method->invokeArgs($object, $params);
+    }
 }