remove Countdown

src/components/Countdown/demo/simple.md

----
-order: 0
-title: Simple
----
-
-简单的页头。
-
-````jsx
-import CountDown from 'ant-design-pro/lib/CountDown';
-
-const targetTime = new Date().getTime() + 3900000;
-
-ReactDOM.render(
-  <CountDown target={targetTime} />
-, mountNode);
-````

src/components/Countdown/index.js

-import React, { Component } from 'react';
-
-function fixedZero(val) {
-  return val * 1 < 10 ? `0${val}` : val;
-}
-
-class CountDown extends Component {
-  constructor(props) {
-    super(props);
-
-    const { lastTime } = this.initTime(props);
-
-    this.state = {
-      lastTime,
-    };
-  }
-
-  componentDidMount() {
-    this.tick();
-  }
-
-  componentWillReceiveProps(nextProps) {
-    if (this.props.target !== nextProps.target) {
-      const { lastTime } = this.initTime(nextProps);
-      this.setState({
-        lastTime,
-      });
-    }
-  }
-
-  componentWillUnmount() {
-    clearTimeout(this.timer);
-  }
-
-  timer = 0;
-  interval = 1000;
-  initTime = (props) => {
-    let lastTime = 0;
-    let targetTime = 0;
-    try {
-      if (Object.prototype.toString.call(props.target) === '[object Date]') {
-        targetTime = props.target.getTime();
-      } else {
-        targetTime = new Date(props.target).getTime();
-      }
-    } catch (e) {
-      throw new Error('invalid target prop', e);
-    }
-
-    lastTime = targetTime - new Date().getTime();
-
-    return {
-      lastTime,
-    };
-  }
-  // defaultFormat = time => (
-  //  <span>{moment(time).format('hh:mm:ss')}</span>
-  // );
-  defaultFormat = (time) => {
-    const hours = 60 * 60 * 1000;
-    const minutes = 60 * 1000;
-
-    const h = fixedZero(Math.floor(time / hours));
-    const m = fixedZero(Math.floor((time - (h * hours)) / minutes));
-    const s = fixedZero(Math.floor((time - (h * hours) - (m * minutes)) / 1000));
-    return (
-      <span>{h}:{m}:{s}</span>
-    );
-  }
-  tick = () => {
-    const { onEnd } = this.props;
-    let { lastTime } = this.state;
-
-    this.timer = setTimeout(() => {
-      if (lastTime < this.interval) {
-        clearTimeout(this.timer);
-        this.setState({
-          lastTime: 0,
-        });
-
-        if (onEnd) {
-          onEnd();
-        }
-      } else {
-        lastTime -= this.interval;
-        this.setState({
-          lastTime,
-        });
-
-        this.tick();
-      }
-    }, this.interval);
-  }
-
-  render() {
-    const { format = this.defaultFormat } = this.props;
-    const { lastTime } = this.state;
-
-    const result = format(lastTime);
-
-    return result;
-  }
-}
-
-export default CountDown;

src/components/Countdown/index.md

----
-category: Components
-type: General
-title: CountDown 
-subtitle: 倒计时
-cols: 1
----
-
-倒计时组件。
-
-## API
-
-| 参数      | 说明                                      | 类型         | 默认值 |
-|----------|------------------------------------------|-------------|-------|
-| format | 时间格式化显示显示 | Function(time) |  |
-| target | 目标时间 | Date | - |