title: Replace abbreviated month name with full name in a column of a dataframe
body: <p>I have a dataframe:</p>
  <pre><code>df_1 = pd.DataFrame({'a':['Jan', 'Feb', 'Mar']})
  </code></pre>
  <p>I want to convert all the abbreviated months in column <code>a</code> to their full name. I can do so using a <code>dict</code></p>
  <pre><code>df_1.replace({'a' : { 'Jan' : &quot;January&quot;, 'Feb' : &quot;February&quot;, 'Mar' : &quot;March&quot; }})
  </code></pre>
  <p>But I was wondering if there was a way to do so using the pandas datetime functionality and without having to type out the names of all the months</p>