Cox model support not working

[deaneckles]

It seems like model='cox' is not actually supported because predict.sgd doesn't know how to handle it, despite sgd accepting it.

sgd/R/predict.sgd.R

Lines 23 to 26 in a256063

	predict.sgd <- function(object, newdata, type="link", ...) {
	if (!(object$model %in% c("lm", "glm", "m"))) {
	stop("'model' not supported")
	}

This then means that the example in https://github.com/airoldilab/sgd/blob/master/demo/cox-regression.R does not work.

Looking forward to trying this nice package with some continuous time data. Thanks!