Add Support for Fish Shell

[trafficone]

Summary of Changes:

• Add Fish option and eval script to cli.py
• Add auto-ntfy-done.fish script (should match auto-ntfy-done.sh in functionality)
• Add Fish shell-integration documentation to README.rst
• Add record of new script to data.py
• Add record of new script to setup.py

Tests performed:

• Installed locally using setup.py install --user
  • Integration Test of Fish functionality
  • Tested Bash functionality is retained

If there's anything else you want/need for this PR, let me know.