code: function (o, cb) {
      if (!o.src) {
        throw new Error('glob missing');
      }
      if (!o.out) {
        throw new Error('output dir missing');
      }
  
      var opts = _.extend({}, defaults, o);
      if (opts.style && path.basename(opts.style).indexOf('.') === -1) {
        opts.style = path.join(opts.style, replaceExtension(opts.name, '.' + opts.processor));
      }
      vfs.src(opts.src)
        .pipe(sprite(opts))
        .pipe(through2.obj(writeFile))
        .on('data', noop)
        .on('end', function () {
          if (_.isFunction(cb)) {
            cb();
          }
        });
    }
docs: /*
  Creates sprite and css file