usdata (development version)

usdata 0.1.0

Added a NEWS.md file to track changes to the package.
Added 10 datasets: county_complete, county, govrace10, houserace10, prrace08, senaterace10, state_stats, urban_owner, urban_rural_pop, vote_nsa, previously hosted in the openintro package.
Added 2 functions: abbr2state, state2abbr, previously hosted in the openintro package.