[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/loading/index.vue

@@ -1,6 +1,6 @@
 <template>
-  <div :class="['van-loading', 'van-loading--' + type, 'van-loading--' + color]">
-    <span :class="['van-loading__spinner', 'van-loading__spinner--' + type, 'van-loading__spinner--' + color]">
+  <div class="van-loading" :class="['van-loading--' + type, 'van-loading--' + color]">
+    <span class="van-loading__spinner" :class="['van-loading__spinner--' + type, 'van-loading__spinner--' + color]">
       <i v-if="type === 'spinner'" v-for="item in 12" />
     </span>
   </div>