Tweak wording in the example about <center>.

Author: tabatkins

css3-flexbox/Overview.html

@@ -1472,8 +1472,8 @@ <h3 id=flex-align><span class=secno>5.2. </span> Cross Axis Alignment: the
 
   <div class=example>
    <p>By using a vertical flexbox and &lsquo;<a href="#flex-align0"><code
-    class=property>flex-align</code></a>&rsquo;, we can emulate the
-    functionality of HTML's <code>&lt;center></code> element:</p>
+    class=property>flex-align</code></a>&rsquo;, we can achieve behavior very
+    close to HTML's <code>&lt;center></code> element:</p>
 
    <div class=code-and-figure>
     <div>

css3-flexbox/Overview.src.html

@@ -694,7 +694,7 @@ <h3 id='flex-align'>
 	</div>
 
 	<div class=example>   
-		<p>By using a vertical flexbox and 'flex-align', we can emulate the functionality of HTML's <code>&lt;center></code> element:</p>
+		<p>By using a vertical flexbox and 'flex-align', we can achieve behavior very close to HTML's <code>&lt;center></code> element:</p>
 
 		<div class='code-and-figure'>
 			<div><pre>