Set up localization

views/login.erb

@@ -1,14 +1,14 @@
-<h1>Log in</h1>
+<h1><%= _("Login") %></h1>
 <% if @error %>
   <p class="error"><%= @error %></p>
 <% end %>
 <form action="/login" method="POST">
   <p>
-    <label for="email">Email</label>
+    <label for="email"><%= _("Email") %></label>
     <input type="text" name="email">
   </p>
   <p>
-    <label for="password">Password</label>
+    <label for="password"><%= _("Password") %></label>
     <input type="password" name="password">
   </p>
   <button type="submit">Log in</button>