Uploader: Extract Uploader from Markdown Renderer.

Usage
-----

1. Uploader: Call fileUploader javascript function with uploader div,
editor textarea and url to the container of files. (e.g. "/files")

    fileUploader($('#upload-form'), $('#body'),
        "@routes.AttachmentApp.newFile");

2. Downloader: Call fileDownloader javascript function with downloader
div and url to the container of files. (e.g. "/files")

    fileDownloader($('.body-attachments'),
        "@routes.AttachmentApp.getFileList");