title: Chartkick y axis uncorrect labeling
body: <p>I have chartkick 1.2.0 and groupdate 1.0.4 gem installed. When I try to do sth like: </p>
  
  <pre><code>  &lt;%= area_chart Match.group_by_day_of_week(:created_at).count, :width=&gt;"700px;", :height=&gt;"150px;"  %&gt;
  </code></pre>
  
  <p>I get this:</p>
  
  <p><img src="https://i.stack.imgur.com/9VuPw.png" alt="enter image description here"></p>
  
  <p>It always gives me the wrong y-axis. How should I format it so that it would display "Monday", "Tuesday" ...</p>
  
  <p>My second example which I also can't get it right is grouping by hours in a day.</p>
  
  <pre><code>  &lt;% abc=Matches.on_location(@location).group_by{|b| b.created_at.strftime("%H").to_i} %&gt;
    &lt;% abc.update(abc){|key, v| v.length} %&gt;
    &lt;%= abc=abc.sort_by{|k,v| k} %&gt;
    &lt;%= area_chart abc, :width=&gt;"700px;", :height=&gt;"150px;"  %&gt;
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/oUqos.png" alt=""></p>
  
  <p>What am I doing wrong, that it displays 1:00:00 AM etc? I would just like to have numbers ie.: 0, 1, 2, 3 .. 23?</p>
  
  <p>I googled around, checked their docs top to bottom: <a href="http://ankane.github.io/chartkick/" rel="nofollow noreferrer">http://ankane.github.io/chartkick/</a> for some hours now and I really don't know what have I missed. Any help would be greatly appreciated!</p>