func RemoveByIndex in DoublyLinkedList.go has a problem

[renyucheng]

the block below has a problem that the previous head can still be referred to

if i == 0 {
	list.head.prev = nil
	list.head = list.head.next
	return true
}

it should be like this

if i == 0 {
	list.head = list.head.next
        list.head.prev = nil
	return true
}