reports crash if user's name is non-ASCII

1. edit ~/.gtimelog/gtimelogrc, specify name = ☻ or anything else with non-ASCII characters
2. start gtimelog
3. try to send a report

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/gtimelog/main.py", line 1858, in on_weekly_report_activate
    self.mail(report)
  File "/usr/lib/python2.7/dist-packages/gtimelog/main.py", line 1948, in mail
    write_draft(draft, self.settings.email, self.settings.name)
  File "/usr/lib/python2.7/dist-packages/gtimelog/main.py", line 724, in weekly_report_plain
    estimated_column=estimated_column)
  File "/usr/lib/python2.7/dist-packages/gtimelog/main.py", line 657, in _plain_report
    print >> output, 'Subject: %s' % subject
  File "/usr/lib/python2.7/codecs.py", line 691, in write
    return self.writer.write(data)
  File "/usr/lib/python2.7/codecs.py", line 351, in write
    data, consumed = self.encode(object, self.errors)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe2 in position 34: ordinal not in range(128)