Add endpoint that returns a single town in the urban region of a state

[theterminalguy]

URL: api/v2/states/:state_id/urban/towns/:town_id or api/v2/states/:state_name/urban/towns/:town_id or api/v2/states/:state_code/urban/towns/:town_id
Parameters: state_id/urban/towns/:town_id or state_name/urban/towns/:town_id or state_code/urban/towns/:town_id
Response(200)

{
  id: 1, 
  state: "Ab", 
  towns: 
    [
      {id: 1, name: "Umahia"}, 
      {id: 2, name: "Aba"}
    ]
}

For more details, check https://github.com/devcenter-square/states-and-cities/wiki/List-of-Endpoints