[improvement] Tab: optimize transition (#2151)

packages/tabs/index.less

@@ -3,6 +3,7 @@
 .van-tab {
   flex: 1;
   cursor: pointer;
+  min-width: 0; // hack for flex ellipsis
   padding: 0 5px;
   font-size: 14px;
   position: relative;
@@ -11,7 +12,7 @@
   text-align: center;
   box-sizing: border-box;
   background-color: @white;
-  min-width: 0; /* hack for flex ellipsis */
+  transition: color .3s;
 
   span {
     display: block;

packages/tabs/index.vue

@@ -72,6 +72,7 @@ export default create({
   props: {
     color: String,
     sticky: Boolean,
+    animated: Boolean,
     lineWidth: Number,
     swipeable: Boolean,
     active: {
@@ -84,7 +85,7 @@ export default create({
     },
     duration: {
       type: Number,
-      default: 0.4
+      default: 0.3
     },
     swipeThreshold: {
       type: Number,
@@ -93,8 +94,7 @@ export default create({
     offsetTop: {
       type: Number,
       default: 0
-    },
-    animated: Boolean
+    }
   },
 
   data() {