<h1>Log In</h1>

<div class="row">
  <div class="col-md-6 col-md-offset-3">
	 <%= form_for(:session, url: sessions_path) do |f| %>
      <div class="field">
      <%= f.label :username %>
      <%= f.email_field :username, class: '' %>
      </div>
      <div class="field">		
      <%= f.label :password %>
      <%= f.password_field :password, class: '' %>
      </div>
      
      <%= f.submit "Log in", class: "btn btn-primary" %>
    <% end %>
  </div>
</div>
<h1>Log In</h1>

<div class="row">
  <div class="col-md-6 col-md-offset-3">
	 <%= form_for(:session, url: sessions_path) do |f| %>
      <div class="field">
      <%= f.label :username %>
      <%= f.text_field :username, class: '' %>
      </div>
      <div class="field">		
      <%= f.label :password %>
      <%= f.password_field :password, class: '' %>
      </div>
      
      <%= f.submit "Log in", class: "btn btn-primary" %>
    <% end %>
  </div>
</div>
Change email field to text field
Change email field to text field
