Fix button text whitespace

components/date-picker/demo/locale.md

@@ -17,7 +17,7 @@ const App = React.createClass({
       locale: assign({}, enUS, {
         timezoneOffset: 0 * 60,
         firstDayOfWeek: 0,
-        minimalDaysInFirstWeek: 1
+        minimalDaysInFirstWeek: 1,
       })
     };
   },

components/date-picker/locale/zh_CN.js

@@ -9,6 +9,9 @@ locale.lang = objectAssign({
   timePlaceholder: '请选择时间',
 }, CalendarLocale);
 
+// should add whitespace between char in Button
+locale.lang.ok = '确 定';
+
 // All settings at:
 // https://github.com/ant-design/ant-design/issues/424