Fix for loop with reversed and limit.

    # array being [1,2,3]
    for item in array reversed limit:2

currently returns [2,1]. This fix makes it more logically: [3,2].
This is an in place operation on the collection itself, which seems like it could have some nasty side effects.  Also, the collection may not be an array at this point, since `Utils.slice_collection` supports anything with the method `each` (see Liquid::Utils.slice_collection_using_each).