Merge pull request #160 from matrix-org/daniel/optional

Note that invite_room_state is optional

event-schemas/schema/v1/m.room.member

@@ -1,7 +1,7 @@
 {
     "type": "object",
     "title": "The current membership state of a user in the room.",
-    "description": "Adjusts the membership state for a user in a room. It is preferable to use the membership APIs (``/rooms/<room id>/invite`` etc) when performing membership actions rather than adjusting the state directly as there are a restricted set of valid transformations. For example, user A cannot force user B to join a room, and trying to force this state change directly will fail. \n\nThe ``third_party_invite`` property will be set if this invite is an ``invite`` event and is the successor of an ``m.room.third_party_invite`` event, and absent otherwise.\n\nThis event also includes an ``invite_room_state`` key **outside the** ``content`` **key**. This contains an array of ``StrippedState`` Events. These events provide information on a few select state events such as the room name.",
+    "description": "Adjusts the membership state for a user in a room. It is preferable to use the membership APIs (``/rooms/<room id>/invite`` etc) when performing membership actions rather than adjusting the state directly as there are a restricted set of valid transformations. For example, user A cannot force user B to join a room, and trying to force this state change directly will fail. \n\nThe ``third_party_invite`` property will be set if this invite is an ``invite`` event and is the successor of an ``m.room.third_party_invite`` event, and absent otherwise.\n\nThis event may also include an ``invite_room_state`` key **outside the** ``content`` **key**. If present, this contains an array of ``StrippedState`` Events. These events provide information on a few select state events such as the room name.",
     "allOf": [{
         "$ref": "core-event-schema/state_event.json"
     }],