squid-report

## adding a new rule (checklist)

1. add a new unit-test module for your rule in tests/rules/
2. (optional: add positive and negative log files)
3. add a new module in squidreport/rules
4. subclass BaseRule and make sure it has a unique code property
5. import your new rule in squidreport/rules/__init__.py
6. add your new rule in ALL_RULES