title: Why was session_store.rb removed in Rails 5.1?
body: <p>Rails 5.1 removes the <code>config/initializers/session_store.rb</code> file.  The <a href="http://guides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-5-0-to-rails-5-1" rel="nofollow noreferrer">upgrading guide</a> doesn't mention it.  Can someone explain why it was removed and what we should do with our existing file?  My current file looks like the following:</p>
  
  <pre><code>Rails.application.config.session_store(
    :cookie_store,
    :key =&gt; '_foo_session', # any value
    :secure =&gt; Rails.env.production? || Rails.env.staging?, # Only send cookie over SSL when in production and staging
    :http_only =&gt; true # Don't allow Javascript to access the cookie (mitigates cookie-based XSS exploits)
  )
  </code></pre>