Nodes: reservoir computing

Reservoir computing (RC) nodes

LinearReadout(num_unit, **kwargs)	Linear readout node.
NVAR(delay[, order, stride, constant, trainable])	Nonlinear vector auto-regression (NVAR) node.
Reservoir(num_unit[, leaky_rate, ...])	Reservoir node, a pool of leaky-integrator neurons with random recurrent connections [1]_.