Support for CJK characters.

[kimdwkimdw]

Many asian IRC servers support CJK characters in nicknames.

From RFC2812(https://tools.ietf.org/html/rfc2812#section-2.3.1), nickname should be

nickname   =  ( letter / special ) *8( letter / digit / special / "-" )
letter     =  %x41-5A / %x61-7A       ; A-Z / a-z
digit      =  %x30-39                 ; 0-9 
hexdigit   =  digit / "A" / "B" / "C" / "D" / "E" / "F"
special    =  %x5B-60 / %x7B-7D
                 ; "[", "]", "\", "`", "_", "^", "{", "|", "}"

But, I think RFC2812 is too old, and it should support other unicode characters.

I found issue #104 closed several years ago. @outsideris reported it.

I put the regexp generated from http://apps.timwhitlock.info/js/regex#, it contains CJK(Chinese, Japanese, Korean) regexp.

[outsideris]

👍

[simnalamburt]

+1 For this.