PR for issue #71 (Feature request) (#74)

* Added functionality whichs saves the notes to file system as well

* Added timestamp to folder name to allow duplicated code note tiltes in filesystem

* Added first tests for note creation including check if note exists in filesystem

* Made some simplifications regarding file system management wih help of fs-extra

* Added tests

* Changed dependency version

* Changed fs extra version

Author: marvpaul