title: Bundler claims to install current version of formtastic, but bundle open shows it contains deprecated method that should have been removed already
body: <p>First time posting on SO, please forgive me and let me know if there's anything I can do to make this question better.</p>
  
  <p>I'm working on a rails 4 app using the formtastic gem. When I put a boolean input in my form, requesting the page throws an error:</p>
  
  <pre><code>undefined method `check_box_checked?' for ActionView::Helpers::InstanceTag:Class
  </code></pre>
  
  <p>Googling uncovered this PR which should have removed the deprecated method 'check_box_checked?' months ago: <a href="https://github.com/justinfrench/formtastic/pull/915" rel="nofollow">https://github.com/justinfrench/formtastic/pull/915</a></p>
  
  <p>Here's the output of bundle show</p>
  
  <pre><code>djhrtmn@porygon:~/dev/casey$ bundle show formtastic
  /home/djhrtmn/.rvm/gems/ruby-2.0.0-p247/gems/formtastic-2.2.1
  </code></pre>
  
  <p>So it looks like I'm using the right version... but when I bundle open the gem 'check_box_checked?' is still there.</p>
  
  <p>Let me know if there's anything else I can do to improve the question...</p>