Add BindHost to prevent random "Connection timed out" errors

Also see: http://b.wardje.eu/2011/12/znc-failing-to-connect.html
ZNC: Update configuration template for znc 1.4

ZNC 1.4 uses a new section within the configuration file to specify
password hash and salt. This requires adding a new Ansible variable
'irc_password_salt'.

Also update the README file to reflect above changes.
Merge pull request #273 from lvillani/znc-1.4

Znc 1.4