Clear version change documentation

The documentation of [RelativeLayout.py] (https://github.com/kivy/kivy/blob/master/kivy/uix/relativelayout.py#L21) says:

    .. versionchanged:: 1.7.0

        Prior to version 1.7.0 The :class:`RelativeLayout` was implemented as a
        :class`FloatLayout` inside a :class:`Scatter`.  This behaviour/widget has
        been renamed to `ScatterLayout`.  The :class:`RelativeLayout` now only
        supports relative position (and cant be roatated or scaled), so that the
        implemetation can be optimized and avoid the heavier calculations from
        :class:`Scatter` (e.g. inverse matrix, recaculating multiple properties,
        etc)

I was struggling why is it that it says it cannot be rotated or scaled?. I had a `Widget` that inherits from `RelativeLayout` in which I was able to `Rotate` and `Scale` without any problem. It took me quite a while to find out that the documentation only refers to multi-touch behaviour.
Merge pull request #1258 from robertour/patch-1

Clear version change documentation