Return distance in Predic func

[ydarma]

In OnlineClust interface, the Predict function should return also the distance to the nearest cluster. This information could be useful to the user.

Predict(elemt Elemt) (Elemt, int, error)

should become

Predict(elemt Elemt) (Elemt, int, float64, error)

[ydarma]

Implementation is trivial : in algo.go:

func (algo *Algo) Predict(elemt Elemt) (pred Elemt, label int, dist float64, err error) {
    var clust Clust
    clust, err = algo.Centroids()

    if err == nil {
        pred, label, dist = clust.Assign(elemt, algo.space)
    }

    return
}