Made navigation bar responsive and fixed margin issue with history

src/index.js

@@ -1,8 +1,4 @@
 import './css/bootstrap.cosmo.min.css';
-// eslint-disable-next-line
-import $ from 'jquery'; 
-// eslint-disable-next-line
-import Popper from 'popper.js'; 
 import 'animate.css/animate.min.css'
 import 'octicons/build/build.css';
 import React from 'react';