json format has changed...

see:
https://groups.google.com/forum/#!searchin/jquery-fileupload/empty/jquer
y-fileupload/0q8PN2v0I28/pOYs76W-VsEJ

and: https://github.com/blueimp/jQuery-File-Upload/wiki/Setup

format:

{"files": [
  {
    "name": "picture1.jpg",
    "size": 902604,
    "url": "http:\/\/example.org\/files\/picture1.jpg",
    "thumbnail_url":
"http:\/\/example.org\/files\/thumbnail\/picture1.jpg",
    "delete_url": "http:\/\/example.org\/files\/picture1.jpg",
    "delete_type": "DELETE"
  },
  {
    "name": "picture2.jpg",
    "size": 841946,
    "url": "http:\/\/example.org\/files\/picture2.jpg",
    "thumbnail_url":
"http:\/\/example.org\/files\/thumbnail\/picture2.jpg",
    "delete_url": "http:\/\/example.org\/files\/picture2.jpg",
    "delete_type": "DELETE"
  }
]}