Updated template for i18n

ref #5

src/templates/sponsoring_contract.html

@@ -7,9 +7,9 @@
   <body>
     <div class="page">
       <p>ID: {{runner.id}}</p>
-      <p>FIRSTNAME: {{runner.firstname}}</p>
-      <p>LASTNAME: {{runner.lastname}}</p>
-      <p>GROUP: {{runner.group.name}}</p>
+      <p>{{__ "firstname"}}: {{runner.firstname}}</p>
+      <p>{__ "lastname"}: {{runner.lastname}}</p>
+      <p>{__ "group"}: {{runner.group.name}}</p>
     </div>
   </body>
 </html>