Make file handler more generic
Make file handler more generic

jupyter/jupyter-js-filebrowser,blink1073/jupyter-js-filebrowser,blink1073/jupyter-js-filebrowser,jupyter/jupyter-js-filebrowser,blink1073/jupyter-js-filebrowser,jupyter/jupyter-js-filebrowser,jupyter/jupyter-js-filebrowser,jupyter/jupyter-js-filebrowser,blink1073/jupyter-js-filebrowser,blink1073/jupyter-js-filebrowser