title: Warning: the lockfile is being updated to Bundler 2, after which you will be unable to return to Bundler 1
body: <p>I put some new gems in my Gemfile and ran <code>bundle install</code>.
  The installation went successfully, but at the end I got this warning:</p>
  
  <blockquote>
    <p>Warning: the lockfile is being updated to Bundler 2, after which you will be unable to return to Bundler 1.</p>
  </blockquote>
  
  <p>What does this mean - I mean it obviously states that the lockfile is being updated to Bundler2 and I wont be able to return to Bundler 1, and yet, should I be concerned about this? Is there any danger of non-compatibility after this? Why is it updated automatically?</p>