Fix usernames being used in place of hostnames.

Closes #355

irc/getters.go

 	result.nick = client.nick
 	result.nickCasefolded = client.nickCasefolded
 	result.username = client.username
-	result.hostname = client.username
+	result.hostname = client.hostname
 	result.realname = client.realname
 	result.nickMask = client.nickMaskString
 	result.nickMaskCasefolded = client.nickMaskCasefolded