[css-align] Block's justify-self:normal should act like 'stretch', not 'start'. Fixes w3c#1437.

Author: tabatkins

css-align/Overview.bs

@@ -1031,7 +1031,7 @@ Inline/Main-Axis Alignment: the 'justify-self' property</h3>
 		<tr>
 			<th>''justify-self/normal'' Behavior
 			<td>
-				Behaves as ''justify-self/start''.
+				Behaves as ''justify-self/stretch''.
 		<tr>
 			<th>Other Details
 			<td>