Updated docs version and version fragment

docs/VERSION

@@ -1 +1 @@
-2.0.0-beta
+2.1.0

docs/sources/versions.html_fragment

@@ -1,2 +1,3 @@
+<li><a class='version' href='/v2.0'>Version v2.1</a></li>
 <li><a class='version' href='/v2.0'>Version v2.0</a></li>
 <li><a class='version' href='/v1.9'>Version v1.9</a></li>