title: compare two arrays if keys match with underscore.js
body: <p>I have an array with permissions from Facebook and an array of the permissions that the user shouldve given:</p>
  
  <pre><code>window.FB.api('/me/permissions', function(perm){                     
      if(perm){
         var given_permissions =  _.keys(perm['data'][0];
         var needed_permissions = ["publish_stream", "email"];
         //now check if given permissions contains needed permissions
      }
  }
  </code></pre>
  
  <p>Now I want to compare if all the <code>needed_permissions</code> are in <code>given_permissions</code>, in an underscore savvy way (without looping two arrays myself and compare values). I saw a <code>_.include</code> method, but this compares an array with a value. I want to return true if all the permissions are available and else a false. I was looking for a nice single line call if possible.</p>
  
  <p>The reason for this is, that <code>FB.login</code> returns true even if the user chooses to cancel the extended permissions. So I need to doublecheck this.</p>