fix "Users" link from doc

Fixes the link to "Users" from "Documentation" (the relative
link was not correct, replace by an absolute one).

Change-Id: I14dd32e7280091bf363701b5979457731cadb9df

www/docs/index.html

@@ -36,7 +36,7 @@
             <nav id="nav">
               <ul>
                 <li><a href="/">Home</a></li>
-		<li><a href="users.html">Users</a></li>
+		<li><a href="../users.html">Users</a></li>
                 <li class="current">
                   <a href=".">Documentation</a>
                   <ul>