Update copyright to include our starting year. (#408)

Author: josh-padnick

_includes/footer.html

@@ -40,7 +40,7 @@ <h3 class="no-anchor">{{ category.title }}</h3>
     <div class="container">
       <div class="row">
         <div class="col-xs-12 text-center">
-          &copy; {{ 'now' | date: "%Y" }} Gruntwork, Inc. All rights reserved.
+          &copy; 2016 - {{ 'now' | date: "%Y" }} Gruntwork, Inc. All rights reserved.
           <div>
           <span style="display:inline-block; margin-right:12px;"><a href="/legal/terms">Terms of Service</a></span>
           <span style="display:inline-block; margin-right:12px;"><a href="/legal/website-terms">Website Terms</a></span>