chore(package): update eslint to version 2.12.0
chore(package): update eslint to version 2.12.0

https://greenkeeper.io/
kumar303/web-ext,rpl/web-ext,kumar303/web-ext,rpl/web-ext,mozilla/web-ext,shubheksha/web-ext,mozilla/web-ext,shubheksha/web-ext