Add a getting-started link to the pub install docs.

Review URL: https://chromiumcodereview.appspot.com//10890014

Author: nex3

src/site/docs/pub-package-manager/pub-install.markdown

@@ -7,6 +7,13 @@ has-permalinks: true
 
 # {{ page.title }}
 
+<aside class="note">
+  <a href="index.html" style="text-align: right;">
+    <i class="icon-hand-right icon-white">&nbsp;</i>
+    Looking for the quick start guide? Get started with pub
+  </a>
+</aside>
+
     $ pub install
 
 This command installs all the dependencies listed in the