fix drag and drop

https://trello.com/card/drug-and-drop-google-chrome/50966697338f63e04a01
6041/191
edit code comment
Merge pull request #26 from uploadcare/drag-and-drop_fix

fix drag and drop
Merge branch 'master' into dialog_step2

* master:
  edit code comment
  fix drag and drop
rescue file info in preview dialog state