Add notes about bot users to API presence documentation

page_presence.md

@@ -1,28 +1,29 @@
 # Presence
 
 A user can have one of two possible presence values, `active` or `away`. A user
-is active if all of the following are true:
+is active if they have at least one client connected to Slack, and they are not
+marked as "away". There are two ways a user can be marked as away: automatic
+and manual.
 
-  * They have at least one client currently connected to Slack.
-  * They have performed an action in the last 30 minutes.
-  * They have not manually set themselves as away (see below).
-
-If any of these conditions are false, the user is away.
+## Automatic Away
 
 The Slack message servers will automatically detect activity based on
-messages sent from a client. However, it's possible to actively use a Slack
-client without causing any messages to be sent; in these situations the client
-should indicate activity has occured by calling the API.
+messages sent from a client. If they detect no messages in 30 minutes, the
+user is marked as automatically away.
 
-Every Slack API method accepts an additional `set_active` argument. This can
-be used to indicate activity has occured while performing the requested
-action.
+However, it's possible to actively use a Slack client without causing any
+messages to be sent; in these situations the client can indicate activity has
+occured by calling the API. Every Slack API method accepts an additional
+`set_active` argument. This can be used to indicate activity has occured while
+performing the requested action.
 
 If the user's activity generates no API calls then the client can periodically
 call [users.setActive](/methods/users.setActive) to let the Slack servers know
 about that activity.
 
-## Manually setting user presence
+These auto-away rules do not apply to [Bot Users](/bot-users).
+
+## Manual Away
 
 An application can call [presence.set](/methods/presence.set)
 to manually mark a user as `away` or `active`. A manual status set using this