Request: Test runner

[DrKain]

I've been delaying this for too long but it's probably something that needs to be done soon.
It's a tricky once you branch out from simply removing tracking parameters, but right now there's a lot more that goes on behind the scene. The goal is still the same: to stop websites tracking you without your permission.

The test runner doesn't need to be too complex but it should cover every different handler used when cleaning, something like ava would be fine but I'm open to other suggestions if anyone has one. Hopefully this will prevent accidentally breaking core functionality in cases like #102, or ensuring any new changes still function correctly.

The test runner should have a range of test URLs that fit every possible modification made to a URL.
You can see a full list of options a rule can have in the wiki:
https://github.com/DrKain/tidy-url/wiki/Creating-Rules

Once implemented all tests must pass before PR a can be merged, this should make things a lot easier for people wanting to contribute and for me reviewing them.