Fix for reverse filter changing original array

Hello,

I've noticed that 'reverse' filter changes original array when used because it uses JavaScript Array's 'reverse' function that modifies the object it's called upon (see [http://jsfiddle.net/2yaj9j8y/](http://jsfiddle.net/2yaj9j8y/)). I've checked with PHP's Twig and it preservers original array, so I've made a few tests and a fix for this. 

Best regards!