enable button when amber loads

_layouts/index.html

@@ -22,6 +22,7 @@
                 'transport.defaultAmdNamespace': "amber/website"
             }).then(function () {
                 document.getElementById('version').innerText = 'v' + amber.globals.Smalltalk._version();
+                document.querySelector('.try button').disabled = false;
             });
         });
     </script>
@@ -109,7 +110,7 @@
         <div class="clear"></div>
 
         <p class="try">
-            <button class="huge" onClick="require('amber/helpers').globals.Browser._open()">Try Amber in your browser!
+            <button class="huge" disabled onClick="require('amber/helpers').globals.Browser._open()">Try Amber in your browser!
             </button>
         </p>