Update nav.html

Author: agibsonccc

_includes/nav.html

@@ -1,4 +1,7 @@
 <nav class="navbar navbar-expand-lg navbar-light navbar-color nav-sticky-top">
+   <div class="container">
+          <a class="nav-item btn btn-rounded btn-outline-warning" href="https://deeplearning4j.konduit.ai/">This site is deprecated. Please migrate to https://deeplearning4j.konduit.ai/</a>
+    </div>
     <div class="search-inline">
         <form>
             <input type="text" class="form-control" placeholder="Type and hit enter...">