fix book link

Author: tony

doc/_templates/book.html

@@ -2,7 +2,7 @@ <h3>Book Pre-order</h3>
 
 <p><img src="https://s3.amazonaws.com/titlepages.leanpub.com/the-tao-of-tmux/large"></p>
 
-<p>Get your copy of the <em>The Tao of tmux</em> on <a class="reference external" href="https://leanpub.com/the-tao-of-tmux">Leanpub</a> and <a class="reference external" href="https://www.amazon.com/gp/product/B01MG342KU/ref=as_li_tl?ie=UTF8&amp;camp=1789&amp;creative=9325&amp;creativeASIN=B01MG342KU&amp;linkCode=as2&amp;tag=gitpull-20&amp;linkId=e6d3f08ad92bfea1cf62d735b6a90bdf">Kindle</a> (Amazon).
+<p>Get your copy of the <em>The Tao of tmux</em> on <a class="reference external" href="https://leanpub.com/the-tao-of-tmux">Leanpub</a> and <a class="reference external" href="http://amzn.to/2gPfRhC">Kindle</a> (Amazon).
 The final version will be delivered to you January 2017.</p>
 <p>Read and browse the book for <a class="reference external" href="https://leanpub.com/the-tao-of-tmux/read">free on the web</a>.</p>
 <a class="reference external image-reference" href="http://amzn.to/2gPfRhC"><img alt="Amazon Kindle" src="https://www.git-pull.com/_images/amazon-logo.png" width="45%"></a>