Setup Babel for ES2017

只測試過async await是可以用的，新的東西不知道會有什麼雷，請自己先想過三次是否要換語言

安裝:
> npm install --save-dev babel-cli babel-preset-es2017
> echo '{ "presets": ["es2017"] }' > .babelrc

測試程式(a.js)如下:

1:  async function Insert(data) {  
2:    return new Promise(resolve => {  
3:      console.log('insert data '+data);  
4:      resolve();  
5:    });  
6:  }  
7:  async function Hello(data_from_client) {  
8:    await Insert(data_from_client);  
9:    await Insert(data_from_client+1);  
10:    await Insert(data_from_client+2);  
11:    console.log('transaction finished');  
12:  };  
13:  Hello(1);  

直接執行:
> babel-node a.js

從ES2017轉舊版js(b.js)
> babel a.js --presets es2017 > b.js

Ubuntu安裝:
需要多安裝一個env套件才有es2015支援
> npm install babel-preset-env --save-dev
> echo '{ "presets": ["env", "es2017"] }' > .babelrc

參考來源:
https://babeljs.io/docs/plugins/preset-es2017/#usage-via-babelrc-recommended