Added a dump raw option

I needed this to allow for piping the output of this command in to another db for remote syncing. I added it as an extra command instead of changing dump as I didn't want to break your api. There may be a nicer way of doing this, perhaps as an option on dump. 

Dump raw for sync works like this 

    ssh -C dokku@SERVER1 mariadb:dumpraw db1 | ssh -C dokku@SERVER2 mariadb:console db1