index.html: Update brew formula name

`mobile-shell` is now `mosh`.

Author: kevinji

Diff for: index.html

@@ -245,7 +245,7 @@ <h3 class="callout"><a href="https://www.apple.com"><img class="logo" src="macos
 
     <div class="span4" style="vertical-align: top;">
       <h3 class="callout"><a href="https://mxcl.github.io/homebrew/"><img class="logo" src="homebrew2.png" alt=""></a>Homebrew <small>OS X 10.5 or later</small></h3>
-            <pre>$ brew install mobile-shell</pre>
+            <pre>$ brew install mosh</pre>
       <br />
     </div>
     <div class="span4" style="vertical-align: top;">