Consistency in geo_value or state_abb or group

[zsusswein]

The data reading functions alternating between calling the geographic groups geo_value, state_abb, or simply group.

We need to pick one name and use it consistently. This change will also have the convenient side effect of allowing us to write a good definition once and @ inheritParams it.

@kgostic @natemcintosh any preferences here?

[athowes]

What does this mean?

[zsusswein]

How's that?

[athowes]

This is good and I have the same issue further up. I think geo_value is better. The "US" is not a state abbreviation.

[zsusswein]

Agreed that geo_value is my preferred answer

[natemcintosh]

Agreed on geo_value

[athowes]

Sounds to me like we are agreed.