Support for non-ASCII character nickname.

[9bow]

Related to #456

Recently I fix the code for detect nick before '!' character. From this line, to match = message.prefix.match(/^([^!]*)(!([^@]+)@(.*))?$/);

This one is very similar with #175 (by @ejnahc), because the PRs above does not catch nickname like 'Αλφαé'(non-CJK characters). This is not strictly fit for RFC, but practically useful for non-ASCII IRC servers (NICKNAME +'!'+ IDENT +'@'+ ADDRESS).