feature/6/view-add-cities

[Lmanning1431]

6. As a user, I want to add a city, so that I can expand service to new areas

• GIVEN a user is viewing any page on the site
• WHEN they click on the "Cities" link in the Nav bar
• THEN they are presented with a list of the current cities
• GIVEN a user is viewing the list of cities
• WHEN they enter a City name in the "Add a city" input and click "Add"
• THEN the city is added to the list of cities