A simple ticket system for Peatio

What's include:

1. Ticket has two status in this version 'open', 'closed'. It could be extended very easily in the future.
2. User could submit the Ticket, then admin could see it on admin panel.
3. Both user and admin can reply on the tickets.
4. read/unread status for the comments.
5. A notification counter to notify the user there are some unread ticket' reply.