[Maintenance] Making a crosswalk app tools release

Laundry list for making a crosswalk-app-tools npm release.

First, ensure that the output of crosswalk-pkg --help reproduced in README.md is up to date.

1. Make sure you are in the collaborators list: https://www.npmjs.com/package/crosswalk-app-tools/access
2. Login: $ npm login
3. Update local clone (master branch): $ git checkout master && git pull
4. Update npm dependencies $ npm install
5. Check in package.json that version number is greater than current published version
6. Make release $ grunt release
7. Open package.json and increment version number
8. Commit updated package.json
9. Push to master including tag created by grunt-release: $ git push --tags

Troubleshooting: If step 6. fails, the already created git tag will make subsequent attempts fail. Remove the tag using $ git tag -d <tag> before retrying.