Make sure that we consistently refer to 'positive/negative flex ratio' everywhere.

Author: tabatkins

css3-flexbox/Overview.src.html

@@ -791,8 +791,8 @@ <h2 id='flexibility'>
 		The defining aspect of flexbox layout is the ability to make the <i>flexbox items</i> "flex", 
 		altering their width or height to fill the available space. 
 		This is done with the 'flex' property. 
-		A flexbox distributes free space to its items proportional to their positive flexibility, 
-		or shrinks them to prevent overflow proportional to their negative flexibility.
+		A flexbox distributes free space to its items proportional to their <i>positive flex ratio</i>, 
+		or shrinks them to prevent overflow proportional to their <i>negative flex ratio</i>.
 
 	<table class=propdef>
 		<tr>
@@ -1683,8 +1683,8 @@ <h3 id='resolve-flexible-lengths'>
 			Sum the hypothetical outer main sizes of all items on the line,
 			clamped according to their min and max main size properties.
 			If the sum is greater than the flexbox's inner main size,
-			use positive flexibility for the rest of this algorithm;
-			otherwise, use negative flexibility.
+			use the <i>positive flex ratio</i> for the rest of this algorithm;
+			otherwise, use the <i>negative flex ratio</i>.
 
 		<li>
 			<strong>Check that you can distribute any space.</strong>