add list filter field, as in main Checkvist application

Hello Luka,

  Hope you're well :)
 
  We've made several changes in embedded presentation of Checkvist lists. 
  The most noticeable thing is that filter field for the list is now available. Also, we've moved "Logout" and "Open my lists in browser" links to the popup under userpic in the header (and I've removed "Open" link from the extension). I've also updated the manifest file according to the latest requirements by Google.

  Currently, you can see those changes at http://beta.checkvist.com/iframe.html 
  We decided to postpone updating of the main checkvist.com site until chrome extension is updated.

  Could you please review my changes and update the chrome extension? After that we'll update the main checkvist.com site.

  Thanks!