title: Send reset_password_instructions manually with devise 3.1.1 rails
body: <p>I am using devise 3.1.1 and trying to send a reset_password_instructions</p>
  
  <pre><code>Devise::Mailer.reset_password_instructions(@user, opts = {}).deliver
  </code></pre>
  
  <p>The mail is been sent but the @token is empty
  I am tracing the @resource and the field reset_password_token is nil, 
  when I am trying to generate a reset_password_token </p>
  
  <pre><code>@user.generate_password_token
  User::generate_password_token
  </code></pre>
  
  <p>Both are giving me a no method error. </p>