s/local_file_fname/local_file_name/

Fix typo.
Remove unused imports
Handle different prefixes of St. Mary's county result

Raw data files from the state use different naming conventions
for  St. Mary's county depending on the vintage.

Prior to 2006, the prefix "Saint_Marys_" is used, e.g.
"Saint_Marys_Republican_Primary_2004.csv". After 2004, it looks like
"St.Marys" is used, e.g. "St.MarysCounty_Republican_2006_Primary".

Update the DataSource implementation to reflect this.

Closes #82
Add reform party to fixture
Remove date-related function and method names

I finished ironing out the vintage-specific differences in loading
and transforming Maryland results, so I can rename some of the
date-specific transform functions and loader classes to be more
general.

Addresses #49