change Mr. Bram's icon to self-hosted one

Author: koron

2018/icon/bram.png

@@ -124,7 +124,7 @@ <h2>Keynote Speakers</h2>
           <div class="col-md-6">
             <h2>Bram Moolenaar</h2>
             <p>The author of Vim</p>
-            <img src="https://avatars2.githubusercontent.com/u/8530623?s=460&v=4" width=236 height="236" />
+            <img src="icon/bram.png" width=236 height="236" />
 
             <p>
             <a href="https://github.com/brammool"><img src="icon/github-icon.png" width="32" height="32" /></a>