[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/markdown/en-US/badge.md

@@ -0,0 +1,50 @@
+## Badge
+
+### Install
+``` javascript
+import { Badge } from 'vant';
+
+Vue.component(Badge.name, Badge);
+```
+
+### Usage
+
+#### Basic Usage
+Use `activeKey` prop to set index of chosen 'badge'
+
+```html
+<van-badge-group :activeKey="activeKey">
+  <van-badge title="Title" @click="onClick"></van-badge>
+  <van-badge title="Title" @click="onClick" info="8"></van-badge>
+  <van-badge title="Title" @click="onClick" info="99"></van-badge>
+  <van-badge title="Title" @click="onClick" info="199"></van-badge>
+</van-badge-group>
+```
+
+``` javascript
+export default {
+  data() {
+    return {
+      activeKey: 0
+    };
+  },
+  methods: {
+    onClick(key) {
+      this.activeKey = key;
+    }
+  }
+};
+```
+
+### BadgeGroup API
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| activeKey | Index of chosen badge | `String | Number` | `0` | - |
+
+### Badge API
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| title | Content | `String` | `''` | - |
+| info | Info Message | `String` | `''` | - |
+| url | Link | `String` | - | - |