chore(package): update webpack to version 1.12.13
chore(package): update webpack to version 1.12.13

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