title: How do I know that a gem is compatible with a version of rails?
body: <p>I'm just getting started with ruby on rails and as I follow the tutorial, there isn't an explanation of how certain gems were gathered and placed in the Gemfile. I've just been copying and pasting them and putting them in my Gemfile and running bundle install. </p>
  
  <p>How does one go about downloading specific versions of gems, and their dependencies as well as making sure that they are compatible with the version of rails I'm using? </p>