test: lint addon tests
Add files in test/addon to the make cpplint
rule and fix up existing
style issues. Tests scraped from doc/api/addon.md are filtered out
because those are predominantly for illustrative purposes.
R=@trevnorris?
Lint CI only because make run-ci
doesn't run add-on tests at the moment: https://jenkins-iojs.nodesource.com/job/node-linter/188/