Rename OpenToday strings in html and css

src/Components/IsNiftyOpenApp/App.css

@@ -47,7 +47,7 @@
   height: 100%;
 }
 
-.App .OpenToday-container {
+.App .OpenXDay-container {
   width: 100%;
   height: 100%;
 }

src/Components/IsNiftyOpenApp/App.tsx

@@ -7,7 +7,7 @@ class IsNiftyOpenApp extends React.Component {
   render() {
     return (
       <div className="App">
-        <div className="OpenToday-container">
+        <div className="OpenXDay-container">
           <OpenXDay question={OpenXDay.OpenOrClose.Open} allHolidays={allHolidays} />
         </div>
       </div>