[new feature] add i18n support (#310)

* fix: Tabbar icon line-height

* [new feature] progress add showPivot prop

* [new feature] TabItem support vue-router

* [new feature] update document header style

* [Doc] add toast english ducoment

* [new feature] add i18n support

* feat: Extract demos from markdown

* feat: Base components demos

* [new feature] complete demo extract & translate

* [fix] text cases

* fix: add deepAssign test cases

* fix: changelog detail

* [new feature] AddressEdit support i18n

docs/demos/views/coupon.vue

@@ -0,0 +1,96 @@
+<template>
+  <demo-section>
+    <demo-block :title="$t('basicUsage')">
+      <van-coupon-cell
+        :coupons="coupons"
+        :chosenCoupon="chosenCoupon"
+        @click="showList = true"
+      />
+
+      <van-popup v-model="showList" position="bottom">
+        <van-coupon-list
+          :coupons="coupons"
+          :chosenCoupon="chosenCoupon"
+          :disabledCoupons="disabledCoupons"
+          @change="onChange"
+          @exchange="onExchange"
+        />
+      </van-popup>
+    </demo-block>
+  </demo-section>
+</template>
+
+<script>
+const coupon = {
+  available: 1,
+  discount: 0,
+  denominations: 150,
+  origin_condition: 0,
+  reason: '',
+  value: 150,
+  condition: '下单立减 1.50 元',
+  name: '新手专用优惠券',
+  start_at: 1489104000,
+  end_at: 1514592000
+};
+
+const discountCoupon = {
+  ...coupon,
+  discount: 88,
+  denominations: 0,
+  origin_condition: 50,
+  value: 12,
+  condition: '下单即享 8.8 折'
+};
+
+const disabledCoupon = {
+  ...coupon,
+  avaliable: 0,
+  reason: '未满足使用门槛'
+};
+
+const disabledDiscountCoupon = {
+  ...discountCoupon,
+  avaliable: 0,
+  reason: '未满足使用门槛'
+};
+
+export default {
+  i18n: {
+    'zh-CN': {
+
+    },
+    'en-US': {
+
+    }
+  },
+
+  data() {
+    return {
+      showList: false,
+      chosenCoupon: -1,
+      coupons: [coupon, discountCoupon],
+      disabledCoupons: [disabledCoupon, disabledDiscountCoupon]
+    };
+  },
+
+  methods: {
+    onChange(index) {
+      this.showList = false;      
+      this.chosenCoupon = index;
+    },
+    onExchange(code) {
+      Toast('兑换成功');
+      this.coupons.push(coupon);
+    }
+  }
+};
+</script>
+
+<style lang="postcss">
+.demo-coupon {
+  .van-popup {
+    height: 100%;
+  }
+}
+</style>