title: Changing column width in R's kable does not change width of headers
body: <p>I am using <strong>kable</strong> to make tables of my data in RMarkdown.  You can supposedly adjust column width using the <strong>column_spec</strong> command, however this seems to adjust only the columns of the data, itself, but does not also adjust the column width of my header row.  So now my headers no longer line up with their associated column of data.</p>
  
  <p>For example:</p>
  
  <pre><code>    y &lt;- knitr::kable(head(mtcars), "html")
      column_spec(y, 1:4, width="5em")
  </code></pre>