Added background style options

public/App.jsx

@@ -22,6 +22,7 @@
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 import React from 'react';
+import Background from './background/Background';
 import Header from './header/Header';
 import Footer from './footer/Footer';
 import { HashRouter, Route, Switch } from 'react-router-dom';
@@ -38,7 +39,8 @@ class App extends React.Component {
   render() {
     return (
       <HashRouter>
-        <div className="o-app o-app--style-civil-twilight">
+        <div className="o-app">
+          <Background style="twilight" />
           <Header />
 
           <main className="o-main">