Provit

This version includes many minor improvements. Besides it introduces the browser frontend. It can be invoked, by running *provit browser*.

Changelog:

Added
- filepicker backend
- project directory comments
- provit browser


FIxed

- empty *directories.yaml*
- many errors in the README
- unsafe use of yaml.load()

This version of provit mainly consists of minor improvements and bug fixes such as:

* removed deprecated setuptools dependency
* check directory function added
* added assets
* directory identifier added to provis
* overwrite flag added to provenance class
* directory init function added
* fix exit codes in cli
* added tests