Add more comprehensive testing and fix kcov/coveralls

[cirla]

Use tools like http://gdpr-demo.labs.quantcast.com/user-examples/cookie-workshop.html and http://acdn.origin.appnexus.net/cmp/docs/#/tools/vendor-cookie-decoder to construct more encoding/decoding examples to add more test coverage and test corner cases.

The coverage script in .travis.yml needs to be fixed as it is now only reporting coverage for src/lib.rs and not src/vendor.rs where the actual code lives.