use "naemon.cfg" instead of "nagios.cfg"

fixes "name of main configuration file looks suspicious" if there's an
mistake in configuration. also changed comments.

Signed-off-by: Sven Velt <sven@velt.de>
Merge pull request #11 from wAmpIre/change-cfg-from-nagios-to-naemon

use "naemon.cfg" instead of "nagios.cfg"