Inserir o seguinte código no local desejado para realizar a ação:

 <% if user_signed_in? %>  
  <li>  
  <%= link_to('Logout', destroy_user_session_path, :method => :delete) %>      
  </li>  
 <% else %>  
  <li>  
  <%= link_to "Sign in", new_user_registration_path %>  
  </li>  
  <li>  
  <%= link_to "Sign up", new_user_session_path %>  
  </li>  
 <% end %> 

Inserir o seguinte código no arquivo 'config/initializers/devise.rb':

 config.sign_out_via = :get  

Android: Como colocar um DatePicker no edittext

edtData.setInputType(InputType.TYPE_NULL);  
     edtData.setOnClickListener(new View.OnClickListener() {  
       @Override  
       public void onClick(View v) {  
         Calendar newCalendar = Calendar.getInstance();  
         DatePickerDialog fromDatePickerDialog = new DatePickerDialog(getActivity(), new DatePickerDialog.OnDateSetListener() {  
           public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {  
             SimpleDateFormat dateFormatter = new SimpleDateFormat("dd-MM-yyyy", Locale.US);  
             Calendar newDate = Calendar.getInstance();  
             newDate.set(year, monthOfYear, dayOfMonth);  
             edtData.setText(dateFormatter.format(newDate.getTime()));  
           }  
         },newCalendar.get(Calendar.YEAR), newCalendar.get(Calendar.MONTH), newCalendar.get(Calendar.DAY_OF_MONTH));  
         fromDatePickerDialog.show();  
       }  
     });