python-modernize (https://github.com/mitsuhiko/python-modernize) is a
useful wrapper around 2to3 which comes with sane defaults.

The fixes below were generated by running

    python-modernize --compat-unicode -w .

and then fixing all lint errors.

It was causing problems with Excel, which didn't recognise it and showed
a strange symbol.  I can't find a compelling reason to keep it, so it
goes.

Using example classes from http://docs.python.org/2/library/csv.html#examples

Fixes #390