Pushover support

[helpsterTee]

• New Feature
• Bug Fix

Description

• Implemented new message handling code for python-pushover and extended settings options.

Related Issue

#9

Motivation and Context

Make alternative channel of transportation available for those not using Slack or Twilio

How Has This Been Tested?

• Create Pushover account and application
• Configure settings appropriately
• Start daemon
• Insert USB drive
• Receive notification on mobile device

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.