[css-position-3] Update Changes section.

Author: fantasai

css-position-3/Overview.bs

@@ -1566,11 +1566,8 @@ Acknowledgments</h2>
 Changes since the 3 February 2015 WD</h3>
 
 	The following significant changes were made since the
-	<a href="https://www.w3.org/TR/2015/WD-css3-positioning-20150203/">5 February 2015 Working Draft</a>
+	<a href="https://www.w3.org/TR/2016/WD-css-position-3-20160517/">17 May 2016 Working Draft</a>
 
 	<ul>
-		<li>Added informative table to clarify positioning calculations.
-		<li>Removed “page” and “center” positioning schemes,
-		which had not in fact been approved by the CSSWG
-		and should not have been published in the first place.
+		<li>Rewrote the whole spec for editorial clarity, technical precision, and compatibility with [[CSS-ALIGN-3]], [[CSS-WRITING-MODES-3]], [[CSS-BREAK-3]], and [[CSS-DISPLAY-3]].
 	</ul>