Revert "make update_anc_database.py work with Python 2"

It doesn't even nearly work in Python 2.7.4 because of files versus buffers,
csv expects bytes not unicode, and headers is not a parameter to urllib.urlopen.
Putting it back to Python 3 so I can at least run the script.

This reverts commit d4bc9dbfba54823cef200d8a3623d50dc0f5f4d1.
handle our double-asterisk notation for commissioners with multiple positions

In our google doc we use ** to separate multiple positions in an ANC ("Chair**Treasurer", see 5B).

In update_anc_database.py, turn positions into a list rather than a string. In the template
that renders it, join it back into a nice string.

fixes #71