[Twisted-web] nevow.i18n bugfix and feature need review and commit

[Tommi Virtanen]

Hi. The patches attached to these two bugs need a review
and someone to commit -- I don't have access to my normal
work environment right now.

They do two things:

 - number formatting:
    _('localization with number %d and floats %f') % (42, 3.141)

 - support proper pluralization:
    ungettext('%d dog', '%d dogs', count) % count

http://divmod.org/users/roundup.twistd/nevow/issue212
http://divmod.org/users/roundup.twistd/nevow/issue213