Preliminary script to extract GHCN data set from the GHCN daily dataset

Dependency on the full .dly dataset file found at
ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/daily. Script has only been tested
on the "ghcnd-all.tar.gz", but may work on others. More information
regarding raw data files at
http://www1.ncdc.noaa.gov/pub/data/ghcn/daily/readme.txt
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