remove nagiosgraph mount from readme

[jonnymccullagh]

I fell over this issue today and suggest the readme be updated. Recommending the volume mount for nagiosgraph-etc was added in PR 64.
/opt/nagiosgraph/etc contains the following files by default.

access.conf     labels.conf               nagiosgraph-nagios.cfg  nagiosgraph_fr.conf
datasetdb.conf  map                       nagiosgraph.conf        ngshared.pm
groupdb.conf    nagiosgraph-apache.conf   nagiosgraph_de.conf     rrdopts.conf
hostdb.conf     nagiosgraph-commands.cfg  nagiosgraph_es.conf     servdb.conf

Mounting an empty volume at that location hides these files. I would suggest that new users do not want that to happen and experienced users will be able to copy those files out before mounting a volume over it.

[JasonRivers]

Sorry for the very long delay, Would it be better to do the same as we do for Nagios config - if the directory is empty, then we copy the default files in to place?

[jonnymccullagh]

Yes that sounds great