Use matterbridge vendored slack

vendor/github.com/nlopes/slack/conversation.go

@@ -1,37 +0,0 @@
-package slack
-
-// Conversation is the foundation for IM and BaseGroupConversation
-type conversation struct {
-	ID                 string   `json:"id"`
-	Created            JSONTime `json:"created"`
-	IsOpen             bool     `json:"is_open"`
-	LastRead           string   `json:"last_read,omitempty"`
-	Latest             *Message `json:"latest,omitempty"`
-	UnreadCount        int      `json:"unread_count,omitempty"`
-	UnreadCountDisplay int      `json:"unread_count_display,omitempty"`
-}
-
-// GroupConversation is the foundation for Group and Channel
-type groupConversation struct {
-	conversation
-	Name       string   `json:"name"`
-	Creator    string   `json:"creator"`
-	IsArchived bool     `json:"is_archived"`
-	Members    []string `json:"members"`
-	Topic      Topic    `json:"topic"`
-	Purpose    Purpose  `json:"purpose"`
-}
-
-// Topic contains information about the topic
-type Topic struct {
-	Value   string   `json:"value"`
-	Creator string   `json:"creator"`
-	LastSet JSONTime `json:"last_set"`
-}
-
-// Purpose contains information about the purpose
-type Purpose struct {
-	Value   string   `json:"value"`
-	Creator string   `json:"creator"`
-	LastSet JSONTime `json:"last_set"`
-}