Simple parallel server cluster management tool for Node using ssh and scp. Specify an ssh or scp command and it will run on all servers in the cluster in parallel. If a command was not successful, shync callbacks will receive the return code of the command that was run as the err paramater. shync treats the success of a command as "all or nothing." If the command was successful on all remote machines, null is returned to the callback. If even one machine returned a non 0 code, then the command as a whole is deemed to have failed and the non 0 code will be returned as the err param to the callback.