code: function bumpLevel(level) {
    return gulp.src(config.pkg)
        .pipe(bump({type: level}))
        .on('error', (e) => log.error(e))
        .pipe(gulp.dest(config.root));
  }
docs: Update version in number in `package.json` file.
  
  @param {string} level The semver level identifier (`major`, `minor` or `patch`).
  @return {WritableStream} The stream pipeline.