Return is now by reference & there is a performance test.

Uses a single generator to allow easy construction of an ND point from
pseudo-random numbers thereby presenting a cleaner interface inline with
the other ND generators.

The Vates quantification requires using the Sobol sequence for producing
a point in ND space. The interface as it was made it difficult to
swap out other random number generators. There is now a generic ND
interface that returns a vector of numbers.