message: Fix wrong npm version.
diff: {
  "name": "polymer-build",
  - "version": "3.0.0-pre.6",
  + "version": "3.0.0-pre.7",
  "description": "A library of Gulp build tasks",
  "main": "lib/polymer-build.js",
  "typings": "lib/polymer-build.d.ts",
  