docs: function Tasks(tasks, cwd){
    this.num = 0;
    this.finish = 0;
    var _this = this;
    this.setMaxListeners(50);
    
    forEach(tasks, function(task){
      var exec = require('./' + task.task);
      forEach(task.files, function(file){
        var cmd = new exec({'file': file, cwd: cwd});
        //console.log('[task ' + task.task + '] on file ' + file + ' begin');
        this.num = this.num + 1;
        cmd.on('finish', function(e){
          _this.emit('finish', {ret: e, file: file, task: task.task});
        });
      }, this);
    }, this);
    this._bind();
  }