mod_mam: Improve the README file a bit

mod_mam/README.txt

@@ -8,14 +8,16 @@
 	DESCRIPTION
 	-----------
 
-This module implements Message Archive Management (XEP-0313).
+This module implements XEP-0313: Message Archive Management (MAM).  MAM
+provides server-side storage of messages, which allows for proper
+synchronization of multiple clients.
 
 
 	CONFIGURATION
 	-------------
 
 In order to use this module with the default settings, add the following
-line to the modules section of your ejabberd.yml file:
+line to the 'modules' section of your ejabberd.yml file:
 
   mod_mam: {}
 
@@ -26,7 +28,8 @@ The configurable options are:
   This option defines which access rule is used to limit the maximum number
   of MAM messages a user can have.  That rule should either yield 0, which
   disables MAM storage for the corresponding user(s), or a positive number,
-  or 'infinity' (which is the default).
+  or 'infinity' (which is the default).  If the limit is exceeded, the
+  oldest MAM message is (silently) discarded when a new one is stored.
 
 - default_page_size (default: 25)
 
@@ -37,8 +40,8 @@ The configurable options are:
 
 - max_page_size (default: 100)
 
-  This option specifies the upper limit of messages transmitted per chunk.
-  If the client requests larger pages, 'max_page_size' is used instead.
+  This option limits the number of messages transmitted per chunk.  If the
+  client requests larger pages, 'max_page_size' is used instead.
 
 - request_activates_archiving (default: 'true')
 
@@ -51,4 +54,4 @@ The configurable options are:
 
   The module also supports the 'iqdisc' option, as documented here:
 
-  http://www.process-one.net/docs/ejabberd/guide_en.html#modiqdiscoption
+  https://www.process-one.net/docs/ejabberd/guide_en.html#modiqdiscoption