Retire semantic_form_for

Also a buttload of form cleanups...

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

@@ -6,14 +6,7 @@
           %h3.panel-title
             Sign In
         .panel-body
-          = semantic_form_for(resource, as: resource_name, url: session_path(resource_name)) do |f|
-            = f.input :login
-            = f.input :password
-            - if devise_mapping.rememberable?
-              %p.text-right.small
-                = f.label 'Remember me'
-                = f.check_box :remember_me
-            %p.text-right
-              = f.action :submit, as: :button, label: 'Sign In', button_html: {class: 'btn btn-success'}
+          = form_for(resource, as: resource_name, url: session_path(resource_name)) do |f|
+            = render partial: 'form_fields', locals: { f: f }
           = render partial: 'devise/shared/openid'
           = render partial: 'devise/shared/help'