Add attribution for logo (purescript#128)

paf31 · web-flow · commit d06cf6042c13 · 2018-01-28T09:42:39.000-08:00
Closes purescript#127
diff --git a/index.html b/index.html
@@ -222,6 +222,8 @@ <h3>Book</h3>
       <a href="https://twitter.com/purescript"><i class="fa fa-twitter-square"></i></a>
     </p>
     <p class="text-center text-muted"><small>&copy; PureScript 2017</small></p>
+    <p class="text-center text-muted"><small>The PureScript logo by Gareth Hughes is used under the terms of the Creative Commons Attribution 4.0 license.
+</small></p>
   </footer>
 
 </body>
