Switch docker build to rocketchat repository

Switch docker automated build from singli/rocket.chat  to rocketchat/rocket.chat

Author: Sing-Li

Diff for: .travis.yml

@@ -25,7 +25,7 @@ script:
 - sh ./namedemo.sh
 - cd ..
 after_deploy:
-- "curl -H \"Content-Type: application/json\" --data \"{'build': true}\" -X POST https://registry.hub.docker.com/u/singli/rocket.chat/trigger/$PUSHTOKEN/" 
+- "curl -H \"Content-Type: application/json\" --data \"{'build': true}\" -X POST https://registry.hub.docker.com/u/rocketchat/rocket.chat/trigger/$PUSHTOKEN/" 
 deploy:
   provider: s3
   access_key_id: "AKIAIKIA7H7D47KUHYCA"