Implemented language selection by query param

ref #5

src/templates/sponsoring_contract.html

@@ -8,8 +8,8 @@
     <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>{{__ "lastname"}}: {{runner.lastname}}</p>
+      <p>{{__ "group"}}: {{runner.group.name}}</p>
     </div>
   </body>
 </html>