REFACTOR
----------------

### 1. Use Chrome Puppeteer to control WebWechat.

All codes related with WebDriver/Selenium had been removed.

1. This makes the logic simple: no server, no https endpoint, no WebSocket anymore;
1. Removed lots of Classes, like `PuppetWebServer`, `PuppetWebBrowser`,  `PuppetWebBrowserDriver`, `ssl-pem` and `PUppetWebBrowserCookie` ;
1. Removed all the `Xvfb` packages and settings;

### 2. Upgrade CircleCI from v1 to v2.

Nothing changed except all the YAML syntax of the CircleCI configuration file.

Workflows look very good, maybe set it up later.

### 3. Dockerfile switch from `alpine` to `node:7` image

The size increased hugely. However, this will let us feel better if we want to add more and more packages into our Docker Image: Debian has better support to the packaging ecosystem.

### 4. Drop Node.js v6 support

No special reasons, it's just tooold.

### 5. Use `blue-tape` to do unit testing, with Typing support.

Do not use AVA anymore, do not wait for TAP anymore. They all support TypeScript not well.

### 6. Separate source code related with `watchdog` to a new NPM module.

It's modulized very well and can be used as needed everywhere: https://github.com/zixia/watchdog

### 7. Created a new module `RxQueue` for `throttle` / `debounce` / `delay` tasks.

Consider publishing a solo NPM module in the future.

### 8. Arrange all the WEB JSON data structure

Save them into a single file: `schema.ts`

### 9. A new Class for manage Wechaty Profile

Use it to `new Profile('botName')` and `save()`/`load()`/`get()`/`set` etc.

Closes #839