[TH] recode WI to new XLS data source

I broke some things off into a file_utils.py so
I could start moving some common file functions,
including downloading a remote file, into there.
I don’t know that we’ll stay on the Python solution
long enough for it to matter, but who knows.

WI generates both a city and county data set,
but that’s just based on my cursory reading of
the data source I used. Someone should definitely
research this and see if I captured the correct
data set.
[TH] minor cleanup
Merge pull request #13 from turbovote/wisconsin-fix

Wisconsin fix