[Improvement] optimize staticClass (#337)

* 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

* [bugfix] Search box-sizing wrong

* [Doc] update vant-demo respo

* [Doc] translate theme & demo pages

* [Doc] add Internationalization document

* [bugfix] remove unnecessary props

* [fix] optimize clickoutside

* [new feature] optimize find-parent

* [new feature]: change document title accordinng to language

* [new feature] Pagination code review

* [improvement] adjust icon-font unicode

* [improvement] Icon spinner color inherit

* [improvement] icon default width

* [bugfix] DateTimePicker validate date props

* [bugfix] Tab item text ellipsis

* [improvement] optimize single line ellipsis

* [Improvement] optimzie staticClass

packages/icon/index.vue

@@ -1,5 +1,5 @@
 <template>
-  <i :class="['van-icon', 'van-icon-' + name]" @click="$emit('click', $event)">
+  <i class="van-icon" :class="`van-icon-${name}`" @click="$emit('click', $event)">
     <slot></slot>
   </i>
 </template>