* Update Caddy to 1.0.1, and update import path

This fix updates caddy to 1.0.1 and also
updates the import path to github.com/caddyserver/caddy

This fix fixes 2959
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Also update plugin.cfg
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Update and bump zplugin.go
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>