Include w channel data example in measurement examples

[msweier]

Would be nice to include an example in the documentation with channel_rdb_info parameter to get the expanded channel data.
df_meas_usgs = nwis.get_record(sites=usgs_site, service='measurements', channel_rdb_info='1')

[thodson-usgs]

Hi @msweier, we really need to update the README. nwis.get_record was deprecated awhile ago, in favor of nwis.get_discharge_measurements, etc., but I agree that would be good to document, if you'd like to create a PR.