Implement a 'back' button for going back to welcome screen

[jaskeeratbrar]

Create a 'back' button in results page so as to navigate back to welcome screen.

Task Test:

1. Go to project directory and open readme.md file.
2. Follow the instructions to launch the app.
3. When you launch the app and when you reach the welcome screen, you will see a text field name 'Enter location'.
4. Type location 'Lower Capen' and select the location from drop down menu. Hit the 'Find my Shuttle' button.
5. A new results page showing shuttle timings for 'Lower Capen' should open up.
6. On the top left area of the screen, there should be a 'back' button. Press on it to go back to Welcome screen.