update changes

Author: svgeesus

css-color-4/Overview.bs

@@ -3010,6 +3010,7 @@ Changes</h2>
 <h3 id="changes-from-20160705" class='no-num'>Changes since <a href="http://www.w3.org/TR/2016/WD-css-color-4-20160705/">Working Draft of 05 July 2016</a></h3>
 
 <ul>
+	<li>Changed Lightness in Lab and LCH to be a percentage, for CSS compatibility</li>
 	<li>Clamping of color values clarified</li>
 	<li>Percentage opacity is now allowed</li>
 	<li>Define terms sRGB and linear-light sRGB, for use by other specs</li>