[new feature] Tabbar: add border prop

packages/tabbar/test/__snapshots__/index.spec.js.snap

@@ -1,5 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`disable border 1`] = `<div class="van-tabbar van-tabbar--fixed" style="z-index: 1;"></div>`;
+
 exports[`route mode 1`] = `
 <div class="van-hairline--top-bottom van-tabbar van-tabbar--fixed" style="z-index: 1;">
   <div class="van-tabbar-item van-tabbar-item--active">

packages/tabbar/test/index.spec.js

@@ -112,3 +112,13 @@ test('name prop', () => {
 
   expect(onChange).toHaveBeenCalledWith('b');
 });
+
+test('disable border', () => {
+  const wrapper = mount(Tabbar, {
+    propsData: {
+      border: false
+    }
+  });
+
+  expect(wrapper).toMatchSnapshot();
+});