Update copyright year to say 2019

Author: tumbarumba

docs/_layouts/default.html

@@ -11,7 +11,7 @@
       <span style="float:right;">
         Released under the <a href="http://opensource.org/licenses/BSD-3-Clause">BSD License</a>.
       </span>
-      Copyright 2012-2018 <a href="http://hamcrest.org">hamcrest.org</a>
+      Copyright 2012-2019 <a href="http://hamcrest.org">hamcrest.org</a>
     </footer>
     <a href="http://github.com/hamcrest/JavaHamcrest"><img style="position: absolute; top: 0; right: 0; border: 0;" src="https://s3.amazonaws.com/github/ribbons/forkme_right_green_007200.png" alt="Fork me on GitHub"></a>
   </body>