ie8 and ie9 file upload fixes

* Upgrade to latest stable Fine Uploader
* Fix an ie8 and ie9 bug where responses to file uploads must be of content type 'text/plain'
 (https://github.com/valums/file-uploader/#internet-explorer-limitations)
* Added a customFields option through which we can pass the csrf token to the form uploader because. (fine uploader does not use xhr with ie8 and ie9 for uploads). Had to modify the code of fine uploader slightly, but a PR to their repo will be issued shortly as well.