appropriating Shailen's excellent Futures intro into tutorial

src/site/docs/tutorials/fetchdata/index.markdown

Index: src/site/docs/tutorials/fetchdata/index.markdown
diff --git a/src/site/docs/tutorials/fetchdata/index.markdown b/src/site/docs/tutorials/fetchdata/index.markdown
index 4c3fe8bca70109d0ff7ad468de14ea8c1c6858d5..9687c56a4b26fb143be5def79779bae736ff0e2f 100644
--- a/src/site/docs/tutorials/fetchdata/index.markdown
+++ b/src/site/docs/tutorials/fetchdata/index.markdown
@@ -7,8 +7,8 @@ tutorial:
   id: fetchdata
 next: forms/
 next-title: "Get Input from a Form"
-prev: polymer-intro/
-prev-title: "Define a Custom Element"
+prev: futures/
+prev-title: "Use Future-Based APIs"
 ---
 
 {% capture whats_the_point %}
@@ -297,7 +297,12 @@ to request the file from the server.
      alt="Use the getString() function to make a request">
 
 The getString() method uses a Future object to handle the request.
-You can use the code above as an idiom
+A Future is a way to perform potentially time-consuming operations,
+such as HTTP requests, asynchronously.
+If you haven't encountered Futures yet,
+you can learn more about them in
+[Use Future-Based APIs](/docs/tutorials/futures/).
+Until then, you can use the code above as an idiom
 and provide your own code for the body of the processString() function
 and your own code to handle the error.
 
@@ -462,9 +467,14 @@ Check out Chris Buckett's article,
 for more information and an example with source code for both
 client and server programs.
 
-##What Next?
+##What next?
 
-The next tutorial,
+* If you skipped the previous tutorial,
+[Use Future-Based APIs](/docs/tutorials/futures/),
+we highly recommend that you go back and learn about Futures
+before going any further.
+
+* The next tutorial,
 [Get Input from a Form](/docs/tutorials/forms/),
 contains a client/server example that
 shows you how to use a form to get data from the user,