[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/card.md

@@ -0,0 +1,61 @@
+## Card
+
+### Install
+``` javascript
+import { Card } from 'vant';
+
+Vue.component(Card.name, Card);
+```
+
+### Usage
+
+#### Basic Usage
+
+```html
+<van-card
+  title="Title"
+  desc="Description"
+  num="2"
+  price="2.00"
+  :thumb="imageURL"
+/>
+```
+
+#### Advanced Usage
+Use `slot` to custom content.
+
+```html
+<van-card
+  title="Title"
+  desc="Description"  
+  num="2"
+  price="2.00"
+  :thumb="imageURL"
+>
+  <div slot="footer">
+    <van-button size="mini">Button</van-button>
+    <van-button size="mini">Button</van-button>
+  </div>
+</van-card>
+```
+
+### API
+
+| Attribute | Description | Type | Default | Accepted Values |
+|-----------|-----------|-----------|-------------|-------------|
+| thumb | Left thumb | `String` | - | - |
+| title | Title | `String` | - | - |
+| desc | Description | `String` | - | - |
+| num | Number of goods | `String | Number` | - | - |
+| price | Price of goods | `String | Number` | - | - |
+| centered | Whether content vertical centered | `String` | `false` | - |
+
+### Slot
+
+| name | Description |
+|-----------|-----------|
+| title | Custom title |
+| desc | Custom description |
+| tags | Custom tags |
+| thumb | Custom thumb |
+| footer | Custom footer |