Doc updates, config file

Author: timvaillancourt

README.rst

@@ -104,6 +104,10 @@ Run a Backup
 
 **Using a Config File**
 
+The tool supports a YAML-based config file for settings. The config file is loaded first and any additional command-line arguments override the file based config values.
+
+An example *(with comments)* of the YAML-based config file is here: `conf/mongodb-consistent-backup.example.conf <conf/mongodb-consistent-backup.example.conf>`__. All available config values are also listed by passing the '--help' fag to the tool.
+
 ::
 
     $ mongodb-consistent-backup --config /etc/mongodb-consistent-backup.yml