MCMC with reversible jump to sample variables for changing model size in BMA
[vin,vout] = jump_g(vin,vout,nvmax)
vin = vector of variable numbers for variables included in the model
vout = vector of variable numbers for variables excluded from the model
nvmax = max # of variable allowed in each model
vin = vector of variable numbers in the new model
vout = vector of variable numbers excluded from the new model