Be Python 3.x-compatible and respect xpath index access methods

[nicklasb]

unicode is undefined in python 3, as everything is unicode there. There are no defined unit tests, so I am not nicely able to test for 2.x-compatibility.

[nicklasb]

I added another commit, this because the current scheme of having the index in the tag name for lists breaks how xpath works, which is a quite serious bug.

The correct xpath way of listing the children of a tag is to do tag/child, and you get all the child nodes that are called child. To access a specific index, use tag/child[position()=1 to get the first child instead.

Therefore, there is no point in having the indices in the tag names, rather it makes it impossible to use xpath as it is. Therefore I propose to call array items "item" instead of the current scheme.