Include #2820 in the changelog

index.html

@@ -2394,7 +2394,14 @@ <h2 id="changelog">Change Log</h2>
 
       <p id="1.10.0">
         <b class="header">1.10.0</b> &mdash; <!--TODO: date--> &mdash; <a href="https://github.com/jashkenas/underscore/compare/1.9.2...1.10.0">Diff</a> &mdash; <a href="https://cdn.rawgit.com/jashkenas/underscore/1.10.0/index.html">Docs</a><br />
-        <ul></ul>
+        <ul>
+          <li>
+            Explicitly states in the documentation, and verifies in the
+            unittests, that <tt>_.sortedIndex(array, value)</tt> always returns
+            the lower bound, i.e., the smallest index, at which <tt>value</tt>
+            may be inserted in <tt>array</tt>.
+          </li>
+        </ul>
       </p>
 
       <p id="1.9.2">