code: function isImage(file) {
          var valid = true,
            // formats = _module.options.formats || ['csv', 'xls', 'zip', 'kml', 'kmz', 'gpx', 'lut', 'stl', 'dxf', 'txt', 'pdf', 'svg', 'doc', 'ppt', 'gif', 'png', 'jpg', 'jpeg'],
            formats = _module.options.formats || ["gif", "png", "jpg", "jpeg"],
            filetype = file.name.split(".")[file.name.split(".").length - 1];
          filetype = filetype.toLowerCase();
          if (formats.indexOf(filetype) === -1) valid = false;
          return valid;
        }
docs: should return whether `e.dataTransfer.files[i]` is valid, defaults to a `true` operation