Removed FileUploadControllerBase(in the middle of improving file
upload).
(refs #12) Replaced the latest version of the dropzone.
(refs #12) Implemented the upload area in preview.hrml.
(refs #12) Change the Markdown notation of images.
(refs #12) Implemented the process of saving image.
(refs #12) Created the helper of the attachment function.
(refs #12) Modified to use the helper of the attachment.
(refs #12) Modified from path to baseURL.
(refs #12) Add acceptedFiles options.
(refs #12) Modified the response status when the file does not exist.
Merge branch 'fileupload'