[COOK-3431] Fix `visudo` file validation test

Signed-off-by: Seth Vargo <sethvargo@gmail.com>
[COOK-3610] Document runas attribute for LWRP

Signed-off-by: Seth Vargo <sethvargo@gmail.com>
[COOK-3572] Add Test Kitchen, Specs, Travis CI

Signed-off-by: Seth Vargo <sethvargo@gmail.com>
Update TESTING.md formatting [ci skip]
Update README.md formatting [ci skip]