fix(DatePicker): Change the default export of DatePikcer.

src/date-picker/index.js

@@ -1,5 +1,10 @@
+
+import DatePicker from './DatePicker';
 import './style/index.less';
 
 export { default as TimeSelect } from './TimeSelect';
 export { default as TimePicker } from './TimePicker';
-export { default as DatePicker } from './DatePicker';
+// export { default as DatePicker } from './DatePicker';
+
+
+export default DatePicker;

src/index.js

@@ -23,7 +23,7 @@ export { default as Paging } from './paging/';
 export { default as Progress } from './progress/';
 export { default as Tooltip } from './tooltip/';
 export { default as Tree } from './tree/';
-export { DatePicker } from './date-picker/';
+export { default as DatePicker } from './date-picker/';
 export { default as TimePicker } from './time-picker/';
 export { default as TimeSelect } from './time-select/';
 export { default as Timestamp } from './timestamp';