修复表单组件样式和单元测试用例 (#7)

* fix: loading small style, search style and dialog style

* fix: scroll to top

* fix mobile scroll

* fix scroll to top

* 文档细节优化

* unit test

* dialog and image-preview unit test

* fix form component style

* fix radio and checkbox style

* fix search component style

test/unit/specs/image-preview.spec.js

@@ -0,0 +1,31 @@
+import ImagePreview from 'packages/image-preview';
+
+describe('ImagePreview', () => {
+  afterEach(() => {
+    const el = document.querySelector('.van-image-preview');
+    if (!el) return;
+    if (el.parentNode) {
+      el.parentNode.removeChild(el);
+    }
+    if (el.__vue__) {
+      el.__vue__.$destroy();
+    }
+  });
+
+  it('create a image preview', (done) => {
+    ImagePreview([
+      'https://img.yzcdn.cn/upload_files/2017/03/14/FmTPs0SeyQaAOSK1rRe1sL8RcwSY.jpeg',
+      'https://img.yzcdn.cn/upload_files/2017/03/15/FvexrWlG_WxtCE9Omo5l27n_mAG_.jpeg'
+    ]);
+
+    expect(document.querySelector('.van-image-preview')).to.exist;
+
+    setTimeout(() => {
+      document.querySelector('.van-swipe-item').click();
+      setTimeout(() => {
+        expect(document.querySelector('.van-image-preview').__vue__.$parent.value).to.be.false;
+        done();
+      }, 500);
+    }, 500);
+  });
+});