Create meteo_lookup.py

[amsmith1109]

This pull request is to add one file under the pysplit directory to expand functionality related to met data discovery. It does not alter any current functionality, but could later be integrated with trajectory_generator.py

meteo_lookup.py provides functionality related to NOAA ARL databases. These features include: Looking up file names individually - arl_file() Retrieve a span of file names - arl_span() Retrieve a list of filenames - arl_list() Details for each archive dataset are saved as a dictionary - arl_datasets Downloading files via FTP - download_meteo_data()

name=='main' is a collection of tests for each function.