Version 0.3.1

  - Fix pathlib error with open() call in Python 3.5
  - Look for config file in /etc/pushbroom if not found in user's home
Bump version number to 0.3.0
Add option to remove empty subdirectories

The RemoveEmpty option (default: true) will remove empty subdirectories
from monitored paths.
Move options into a dict

This makes it easier to add new options in the future.
Create trash directory if it does not exist
Add mypy and typing information
Update systemd files to use a timer
Use pathlib in test
Remove unused test configuration file
Bump version number to v0.2.1
Coerce the Shred option into a boolean
Bump version numbero v0.2.0
Use pathlib for path operations
Update minimum Python version to 3.5
Add pipx instructions to README
Mild refactoring to improve pylint score