Unicode encoding errors on write

[vitorio]

Different from the previous two unicode issues, tested with 0.0.8 in pip and also downloading master from here:

$ ./storified.py vitorio
Traceback (most recent call last):
  File "./storified.py", line 163, in <module>
    storified(args.account_name, args.download_dir)
  File "./storified.py", line 25, in storified
    archive_story(story, archive_dir)
  File "./storified.py", line 48, in archive_story
    rewrite_html(story, story_dir)
  File "./storified.py", line 128, in rewrite_html
    open(html_file, 'w').write(soup.prettify())
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2026' in position 48744: ordinal not in range(128)