title: to_json returns string instead of json in Rails
body: <p>The following piece of code should return a json:</p>
  
  <pre><code>  @series = @series.map do |serie| {
      :name =&gt; serie.name,
      :id =&gt; serie.id
    }
  
    @series.to_json
  </code></pre>
  
  <p>It's return is the following:</p>
  
  <pre><code>"[{\"name\":\"Barra\",\"id\":3},{\"name\":\"Botafogo 1\",\"id\":1},{\"name\":\"Botafogo 2\",\"id\":2},{\"name\":\"Tijuca\",\"id\":4}]"
  </code></pre>
  
  <p>Why is it returning a string instead of a json?</p>
  
  <p>'json' gem is both installed and required at the top of my .rb file</p>