add support for additional variables to cpc.drought dataset
add unit tests for cpc.drought
add note to changelog about cpc drought
add basic unit test & framework for cpc drought dataset
typo
add unit tests for ncdc.gsod module; closes #31
cleanup gsod file fetching: use shared util methods
simplify gsod.get_data signature: start_date -> start, end_date -> end
allow ncdc.gsod.get_data() to accept a single station code
rm unused function
convert begin and end values for station dicts to python datetime.date objects
fix minor rounding issues with float values
allow gsod station queries to be limited by state, country, fips codes and date ranges
add changelog note about ncdc.gsod changes
add changelog note about date and datetime parsing
Merge branch 'cpc-drought'

Conflicts:
	CHANGES
minor doc fix
clean up cpc.drought tests: use a mocked data file
change cpc.drought.get_data() kwargs: start_date -> start; end_date -> end to be consistent
replicate tarfile.open()'s context manager for python 2.6 support