Add Cane

* Can be invoked with `cane` or `thor spec quality`
* Settings are in ./.cane
* Currently allowing violations for our current codebase
* Will fail the build if quality or coverage gets any worse
Set line length to 120, update violations count to match
Reduce coverage to 90%, increase violation to 100
Add guard-cane
Only enforce coverage on full CI run
Merge pull request #333 from RiotGames/cane

Add Cane