code: function(cb) {
      async.series([
        function(next){
          if (!fs.existsSync('./src')) {
            return cb()
          }
          if (!fs.existsSync('./lib')) {
            return fs.mkdir('./lib', next)
          }
          next()
        },
        function(next) {
          exec('cp -urf ./src/* ./lib/', next)
        },
        function(next) {
          compile(function(){
            if (info.pkg.json.scripts && info.pkg.json.scripts.prepublish) {
              exec('npm run prepublish', next)
            } else {
              next()
            }
          })
        }
      ], cb)
    }
docs: copy ./src/* to ./lib/* if src is existed