2 diffrent ruby-kakasi implemntations

[NOKUBI Takatsugu <knok@daionet.gr.jp>]

Currently Debian has the ruby-kakasi package.
The original upstream was hosted in RAA, but it was
closed last year.

OTOH, there is a new ruby binding for KAKASI in
rubygems.
https://rubygems.org/gems/kakasi
https://github.com/knu/kakasi_ffi

It seems a brand new implementation, but the usage
seems almost same.

So my proposal is:

1. remove old package (ruby-kakasi)
2. ITP the new implementation the name as "ruby-kakasi"

Houw about this? Of course changeing diffrent package
name is also other choise.