Refactor and update RocketChat bridge

* Add support for editing/deleting messages
* Add support for uploading files
* Add support for avatars
* Use the Rocket.Chat.Go.SDK
* Use the rest and streaming api

vendor/github.com/matterbridge/Rocket.Chat.Go.SDK/models/permission.go

@@ -0,0 +1,7 @@
+package models
+
+type Permission struct {
+	ID        string   `json:"_id"`
+	UpdatedAt string   `json:"_updatedAt.$date"`
+	Roles     []string `json:"roles"`
+}