2010 Census U.S. Gazetteer file layout changed.

2010 Census U.S. Gazetteer file layout changed.

* weather.py(correlate): The United States Census Bureau altered the
format of their 2010 Gazetteer on August 22, 2012, adding and reordering
a few fields. The previous version of the parser assumed a fixed field
order and ceased to work with the updated data files, so now the order
is inferred from the column headings in the first line of each file
instead.