[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/tabs/index.vue

@@ -1,5 +1,5 @@
 <template>
-  <div class="van-tabs" :class="[`van-tabs--${type}`]">
+  <div class="van-tabs" :class="`van-tabs--${type}`">
     <div class="van-tabs__nav-wrap" v-if="type === 'line' && tabs.length > swipeThreshold">
       <div class="van-tabs__swipe" ref="swipe">
         <div class="van-tabs__nav van-tabs__nav--line">
@@ -20,7 +20,7 @@
     <div
       v-else
       class="van-tabs__nav"
-      :class="[`van-tabs__nav--${this.type}`]"
+      :class="`van-tabs__nav--${this.type}`"
     >
       <div class="van-tabs__nav-bar" :style="navBarStyle" v-if="type === 'line'"></div>
       <div