app/views/devise/sessions/new.html.erb
<div class="sign_in">
<%= simple_form_for(resource, :as => resource_name, :url => session_path(resource_name)) do |f| %>
<h2>Sign in</h2>
<div class="form-inputs">
<%= f.input :email, :required => false, :autofocus => true %>
<%= f.input :password, :required => false %>
<%= f.input :remember_me, :as => :boolean if devise_mapping.rememberable? %>
<%= f.button :submit, "Sign in", class: 'btn btn-success' %>
<%- if devise_mapping.recoverable? && controller_name != 'passwords' %>
<%= link_to "Forgot your password?", new_password_path(resource_name) %><br />
<% end -%>
</div>
<% end %>
<div class="modal-footer">
<%- if devise_mapping.registerable? && controller_name != 'registrations' %>
<%= link_to "Register", new_registration_path(resource_name), class: 'btn btn-primary' %><br />
<% end -%>
</div>
</div>