Merge pull request #168 from SaekiTominaga/fix-atom-link

Fix dead link to Atom spec

Author: dontcallmedom

docs/index.html

@@ -29,7 +29,7 @@ <h2>Tutorials</h2>
 <h2>Specifications</h2>
 
 <ul>
-<li><a href="https://xml2rfc.tools.ietf.org/public/rfc/html/rfc4287.html">Atom 1.0</a></li>
+<li><a href="https://www.rfc-editor.org/rfc/rfc4287">Atom 1.0</a></li>
 <li><a href="rss1.html">RSS 1.0 specification</a></li>
 <li><a href="https://www.rssboard.org/rss-specification">RSS 2.0 specification</a></li>
 </ul>