Update README to reflect the changes to attribute filters

README.md

@@ -147,10 +147,15 @@ Whether the control socket should be read-only or read-write. Choose from `ro`,
 
 #### `freeradius::attr`
 
-Install arbitrary attribute filters from a flat file. These are installed in `/etc/raddb/attr.d`
+Install arbitrary attribute filters from a flat file. These are installed in an appropriate module config directory.
+
+##### `key`
+
+Specify a RADIUS attribute to be the key for this attribute filter. Enter only the string part of the name.
 
 ```puppet
 freeradius::attr { 'eduroamlocal':
+  key    => 'User-Name',
   source => 'puppet:///modules/site_freeradius/eduroamlocal',
 }
 ```