title: pushing item in mongoid array
body: <p>I have a model defined like this :</p>
  
  <pre><code>class Foo
    include ::Mongoid::Document
  
    field :name, type: String
    field :followed_bars, type: Array
    field :favorite_bars, type: Array
  end
  </code></pre>
  
  <p>I created a Foo object like this :</p>
  
  <pre><code>foo = Foo.new(name: "Test")
  foo.save
  </code></pre>
  
  <p>In my DB when I type db.foo.find() I can see the object I just created.
  Then, in my application I'm trying to do this :</p>
  
  <pre><code>foo = Foo.first
  foo.push(:followed_bars, "hello")
  </code></pre>
  
  <p>And every time I'm getting an error : <em>ArgumentError: wrong number of arguments (2 for 1)</em></p>
  
  <p>I'm not sure to understand what am I missing here ?</p>
  
  <p>Thanks in advance for help !</p>
  
  <p>Regards.</p>