Add note to the top of mocking post about new docs

The concepts in the article are still accurate, but not all of the code samples. Hopefully we can update the contents soon, but until then it's good to have a note.

Author: Sashko Stubailo

site/blog/20160419-mocking.md

@@ -6,6 +6,9 @@ date: 19 Apr 2016
 byline: "Jonas Helfer"
 guestBio: engineer at Meteor working on Apollo
 ---
+
+> (Editor’s note — the concepts in this post are accurate, but some the code samples don’t demonstrate new usage patterns. After reading, consult the [graphql-tools docs](http://dev.apollodata.com/tools/graphql-tools/mocking.html) to see how to use mocking today.)
+
 Do you think mocking your backend is always a tedious task? If you do, reading this post might change your mind…
 
 Mocking is the practice of creating a fake version of a component, so that you can develop and test other parts of your application independently. Mocking your backend is a great way to quickly build a prototype of your frontend, and it lets you test your frontend without starting up any servers. API mocking is so useful that a [quick Google search](https://www.google.com/?ion=1&espv=2#q=mock+rest+api) will turn up dozens of expensive products and services that promise to help you.