Adds option -x to exclude certain linting policies
and -w to warn of failure for certain linting policies
if failures are expected.
Updates gitignore to exclude files created when running
tests.
Adds requirements for testing.
Adds unit test for new cli options and test
site-definition.yaml
Documentation for cli options can be found here [0].
[0]-https://review.gerrithub.io/#/c/403216/
Change-Id: I6e905c1ba7a23d0b2fdbf9552bec8a6620ff9731
37b2a31b6f