message: Add source url file to release for AMO
diff: "watch": "webpack --watch",
  "release:amo": "cd distribution && webext submit",
  "release:cws": "cd distribution && webstore upload --auto-publish",
  - "release": "run-s build:minified update-version release:*",
  + "release": "run-s build:minified update-version save-url release:*",
  + "save-url": "echo https://github.com/$TRAVIS_REPO_SLUG/tree/$TRAVIS_COMMIT > distribution/SOURCE_URL",
  "update-version": "VERSION=$(date -u +%y.%-m.%-d.%-H%M); echo $VERSION; dot-json distribution/manifest.json version $VERSION",
  "can-release": "if [ \"$TRAVIS_EVENT_TYPE\" = cron ] && [ $(git rev-list -n 1 --since=\"26 hours ago\" master) ]; then echo :ship-it:; else false; fi"
  },
  