Add submit button contain with custom margin.

app/assets/stylesheets/pages/login.scss

@@ -198,6 +198,10 @@
     font-weight: normal;
   }
+  .submit-container {
+    margin-top: 16px;
+  }
+
   input[type="submit"] {
     @extend .btn-block;
     margin-bottom: 0px;

app/views/devise/sessions/_new_base.html.haml

@@ -12,5 +12,5 @@
         %span Remember me
       .pull-right
         = link_to "Forgot your password?", new_password_path(resource_name)
-  %div.prepend-top-20
+  %div.submit-container
     = f.submit "Sign in", class: "btn btn-save"

app/views/devise/shared/_signup_box.html.haml

@@ -24,7 +24,7 @@
         = recaptcha_tags
       %div
         = f.submit "Register", class: "btn-register btn"
-.clearfix.prepend-top-20
+.clearfix.submit-container
   %p
     %span.light Didn't receive a confirmation email?
     = succeed '.' do