title: Customize Bootstrap 4 media queries in a Rails app
body: <p>I want to customize Bootstrap 4 media queries (add a new xxl media query).</p>
  
  <p>Based on this solution, <a href="https://stackoverflow.com/questions/32545506/bootstrap-4-how-to-use-media-query-mixin">Bootstrap 4 - how to use media query mixin</a>, I try to define new $grid-breakpoints but it doesn't affect Bootstrap behavior.</p>
  
  <p>I have used the gem install of Bootstrap. </p>
  
  <p>It seems that the problem is that Bootstrap doesn't use the new media queries and I don't know how to explicitly include Bootstrap files in my stylesheets (to use Bootstrap mixins and functions). The installation of Bootstrap is located in </p>
  
  <pre><code>/Users/myname/.rvm/gems/ruby-2.4.1/gems/bootstrap-4.0.0.beta2.1
  </code></pre>