Merge pull request #907 from herbie-fp/release-2.1

Release Herbie 2.1, update the news page

Author: pavpanchekha

www/doc/latest

@@ -1 +1 @@
-2.0
+2.1

www/index.html

@@ -79,6 +79,8 @@ <h3>Contribute</h3>
 
 <h2>Herbie Project News</h2>
 <ol id="news">
+  <li><time>17 Jul</time>Today we are releasing <a href="doc/2.1/release-notes.html">Herbie 2.1</a>! This release makes Herbie's generated code&mdash;and Herbie itself&mdash;faster. Try it out!</li>
+  <hr class="yearmark" />
   <li><time>30 Jun</time>We are proud to release <a href="doc/2.0/release-notes.html">Herbie 2.0</a>! This release teaches Herbie to optimize for both accuracy and speed, and includes a complete redesign of Herbie's reports and metrics. Try it out!</li>
   <hr class="yearmark" />
   <li><time>24 Jul</time>Due to a major unforseen issue with our release infrastructure, we are re-releasing <a href="doc/1.5/release-notes.html">Herbie 1.5</a>. If you previously tried to install it and failed, please try again!</li>