redisign using callback to render and show images

views/index.pug

@@ -1,5 +1,5 @@
 extends layout
 
 block content
-  h1 ServiceDock
-  div#stacks
+  div#stacks loading...
+  a#svgStacks download image

views/layout.pug

@@ -9,4 +9,6 @@ html
     script(type="text/javascript", src="/socket.io.js")
     script(type="text/javascript", src="/servicedock.js")
   body
-    block content
+    block content
+    footer
+      div#error