title: downloading yearly data from PNADc with lodowm
body: <p>Is it possible to download yearly data from PNADc using lodown?
  I have tried this already:</p>
  
  <pre><code>pnadc_cat &lt;- subset( pnadc_cat , year == 2015 &amp; interview == '1' )
  </code></pre>
  
  <p>instead of</p>
  
  <pre><code>pnadc_cat &lt;- subset( pnadc_cat , year == 2015 &amp; quarter == '03' )
  </code></pre>
  
  <p>but it didn't work.</p>
  
  <p>And I didn't see any references regarding data per year in the lodown's tips.
  I guess it is because it only downloads the quartely data...but is it possible other way around?</p>
  
  <p>thanks.</p>