title: wkhtmltopdf/wicked_pdf : some external pictures are not displayed
body: <p>I'm trying to export a page in my rails app to a pdf using wkhtmltopdf/wickedpdf (both the latest version, so is rails). However, external images from facebook (obviously with an absolute url) are not displayed : I got the classic empty box with a '?' when pictures are missing. The HTML version is just fine.</p>
  
  <p>I tried with other pictures from other sources, and it worked as expected. Only fb pictures are causing troubles. However I absolutely need those.</p>
  
  <p>Any ideas? Thanks for your time!</p>