How to properly add Google Analytics to a Rails project

_google_analytics.rb

- if Rails.env.production?
  :javascript
    (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
    (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
    m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
    })(window,document,'script','//www.google-analytics.com/analytics.js','ga');

    ga('create', 'UA-19488405-8', {'allowAnchor': true});

- else
  :javascript
    function ga () {
      var params = Array.prototype.slice.call(arguments, ga.length);
      console.log("GoogleAnalytics: " + params);
    };