Fixes and improvements for v1.3 documentation

* Add missing versionadded strings for v1.3
* Add missing versionchanged string for Message.edit
* Consistently use versionadded for attributes
* Consistently use versionchanged for parameters
* Use versionchanged for Bot.is_owner
* Fix references in v1.3 changelog
* Improve grammar in v1.3 changelog

discord/team.py

@@ -49,6 +49,8 @@ class Team:
         The team's owner ID.
     members: List[:class:`TeamMember`]
         A list of the members in the team
+
+    .. versionadded:: 1.3
     """
     __slots__ = ('_state', 'id', 'name', 'icon', 'owner_id', 'members')
 
@@ -95,6 +97,8 @@ class TeamMember(BaseUser):
 
             Returns the team member's name with discriminator.
 
+    .. versionadded:: 1.3
+
     Attributes
     -------------
     name: :class:`str`