chore(package): update babel-loader to version 6.2.6
chore(package): update babel-loader to version 6.2.6

https://greenkeeper.io/
tsl143/addons-frontend,jasonthomas/addons-frontend,aviarypl/mozilla-l10n-addons-frontend,kumar303/addons-frontend,tsl143/addons-frontend,tsl143/addons-frontend,kumar303/addons-frontend,jasonthomas/addons-frontend,jasonthomas/addons-frontend,tsl143/addons-frontend,squarewave/addons-frontend,mozilla/addons-frontend,mozilla/addons-frontend,squarewave/addons-frontend,mozilla/addons-frontend,kumar303/addons-frontend,aviarypl/mozilla-l10n-addons-frontend,aviarypl/mozilla-l10n-addons-frontend,kumar303/addons-frontend,mozilla/addons-frontend,squarewave/addons-frontend,aviarypl/mozilla-l10n-addons-frontend