title: generating barcode for Barby gem under EAN-13
body: <p>While attempting to render in HTML a collection of article barcodes and proceeding incrementally to view the data (relative to other objects on tha page), the controller</p>
  <pre><code>require 'barby/outputter/html_outputter'
  require 'barby/barcode/ean_13'
  </code></pre>
  <p>and the view invokes</p>
  <pre><code>&lt;%= this_barcode = article.barcodes.first.barcode %&gt;
  &lt;%= this_barcode.class %&gt;
  &lt;%# barcode = Barby::EAN13.new(this_barcode) %&gt;
  &lt;%# outputter = Barby::HtmlOutputter.new(barcode) %&gt;
  &lt;%# barcode.to_html.html_safe %&gt;
       [returns as expected]
  8001300303466 String
  </code></pre>
  <p>however, when wanting to get the barcode and uncommenting that element it fails to process because <code>data not valid</code> for the line <code>barcode = Barby::EAN13.new(this_barcode)</code> (also occurs with <code>barcode = Barby::EAN13.new(this_barcode.to_i)</code>)</p>
  <p><strong>note</strong>  possibly on garden path here, as there is confusion with <a href="https://github.com/toretore/barby/wiki/Outputters#html" rel="nofollow noreferrer">what the wiki suggests</a> with<br />
  <code>barcode = Barby::DataMatrix.new(number)</code> as that would generate the error<br />
  <code>uninitialized constant Barby::DataMatrix</code></p>
  <p>How does one ensure the data is correct for proper rendering?</p>