title: Rentrez not accepting quote escaping
body: <p>I'm using R rentrez package to retrieve pubmed information. In general, when pubmed interpreter detects a compound phrase, it automatically adds quotation in order to include searching for exact phrase.
  Nevertheless, this doesn't happens every time, giving some retrieval errors in specific settings. For example, I'm searching for &quot;front 2&quot; and response gives results corresponding to the query:</p>
  <blockquote>
  <p>FRONT[All Fields] AND 2[All Fields]</p>
  </blockquote>
  <p>What I need is it to retrieve:</p>
  <blockquote>
  <p>&quot;FRONT 2&quot;[All Fields]</p>
  </blockquote>
  <p>I've tried using double quotes inside single (and the inverse), scaping quotes and urlencoding them.</p>