Add deploy hook for ZNC

[Xinayder]

I've added a deploy hook to automatically deploy the Let's Encrypt certificate for ZNC. You need to run acme.sh as the same user as ZNC, because otherwise the permissions get borked and ZNC breaks.

The znc.pem file is generated with the certificate key, domain certificate and CA certificate. More info: https://wiki.znc.in/Signed_SSL_certificate

The script, by default, uses /var/lib/znc/.znc as the ZNC home directory and znc as the ZNC user (Arch Linux defaults). The user can override these by setting ZNC_USER and ZNC_DIR variables, which will be saved to account.conf.

[Xinayder]

I've updated the script because _stat checks for user and group ownership. Now, the script will check if the specified ownership string user:group matches the current user, and if the current user is part of the owner group. I've also added checks for cat, _stat and pretty much any shell command I've used.

[Neilpang]

please fix the format errors first https://travis-ci.org/Neilpang/acme.sh/jobs/262050938

[Xinayder]

Should be good to go now, just waiting for Travis to finish the OS X build that got stuck.

[Xinayder]

I think this is ready to be merged. Anything else you want me to change?

[Neilpang]

https://travis-ci.org/Neilpang/acme.sh/jobs/263286268

[Xinayder]

Formatting errors fixed.

[Xinayder]

I'll be rebasing this in the next days to the latest commit in dev so it can be merged.

[Xinayder]

Rebased.

[ldir-EDB0]

Is this likely to be merged?