text: //this is the root react component
  import React from 'react'
  import MainRouter from './MainRouter'
  import { BrowserRouter } from 'react-router-dom'
  import { ThemeProvider } from '@material-ui/styles'
  import theme from './theme'
  import { hot } from 'react-hot-loader'
  //Wrapping in ThemeProvider gives all child components access to Material UI theme
  //wrapping  in BrowserRouter enables front end routing
  //then App renders MainRouter which . . .
  const App = () => {
      return (
          <BrowserRouter>
              <ThemeProvider theme={theme}>
                  <MainRouter/>
              </ThemeProvider>
          </BrowserRouter>
      )
  }
  //hot(module) enables live reloading
  export default hot(module)(App)