Need to detect old data from a station and auto-retrieve data from the nearest
active station.

Need to add methods to the Metar class that will detect if any of the
WeatherConditions are rain, snow, etc.

Possibly specify an option to retrieve a cycle file for a period and return
metar records for each?  Or cache the data internally and provide faster
lookups thereafter?  Cycle files found here:

ftp://weather.noaa.gov/data/observations/metar/cycles/[00Z.TXT]

