[simple mode demo] Slight rewording

Author: marijnh

demo/simplemode.html

@@ -32,7 +32,7 @@
 <h2>Simple Mode Demo</h2>
 
 <p>The <a href="../addon/mode/simple.js"><code>mode/simple</code></a>
-addon allows CodeMirror modes to be specified with a relatively simple
+addon allows CodeMirror modes to be specified using a relatively simple
 declarative format. This format is not as powerful as writing code
 directly against the <a href="../doc/manual.html#modeapi">mode
 interface</a>, but is a lot easier to get started with, and