title: Change variable name in dplyr::count using standard evaluation
body: <p>How do I change the name of the grouping variable in <code>dplyr::count_</code> when it's used in a standard evaluation way</p>
  
  <p>For example if in the final tbl I don't want the var name "Species" but "Type" :</p>
  
  <pre><code>iris %&gt;% 
    group_by("Species") %&gt;% 
    count_("Species")
  
  Source: local data frame [3 x 2]
  
       Species  n
  1     setosa 50
  2 versicolor 50
  3  virginica 50
  </code></pre>
  
  <p>Also I wonder how <code>dplyr::count_</code> works and what this expression is supposed to do ? Do you have an explanation ?</p>
  
  <pre><code>&gt; iris %&gt;% group_by("Species") %&gt;% count_("x = Species")
  Source: local data frame [3 x 2]
  
  x = Species  n
  1      setosa 50
  2  versicolor 50
  3   virginica 50
  </code></pre>
  
  <p>Thanks !</p>