Added area code(s) for each state.

[weirdestnerd]

The database now has a new column called area_code, which is a string of area code(s) for each state. A parser is implemented based on the format of area_code and splits the area_code into two formats: full_area_code - a full list of area code(s) and their corresponding cities, plain_area_code - a list of area code(s) without the cities.