Python 2 and 3 compatibility

[steveluscher]

On MacOS X (El Capitan) I tested that the following works:

pyenv install 2.7
pyenv local 2.7
pip install -r requirements.txt
python ./ExportLists.py export  # works
python ./ImportLists.py /path/to/素晴らしい音楽.csv  # works

pyenv install 3.5.1
pyenv local 3.5.1
pip install -r requirements.txt
python ./ExportLists.py export  # works
python ./ImportLists.py /path/to/素晴らしい音楽.csv  # works

Closes #41.

[arcsector]

This should really be merged...