title: check if url can be loaded in an iframe
body: <p>Snip.ly nicely checks if the entered web address can be used in an iframe.
  I'd like to replicate it in ruby. Looking through their code they send an ajax request to their server and thats where they do the validation.</p>
  
  <p>Even after extensive googling couldn't find anything that could help me accomplish that.</p>
  
  <p>My use case is that we let users add news listings to their page, which are shown in iframes, and would like to show it if the entered url can be used in an iframe.</p>