Change NS() to return a vectorized function

[wch]

Previously, NS had this behavior:

ns <- NS(c("one", "two"))
ns(c("three", "four"))
# [1] "one-two-three-four"

But it make more sense for the ns() function (the one which was returned by NS()) to return a vector. Now it does this:

ns <- NS(c("one", "two"))
ns(c("three", "four"))
# [1] "one-two-three" "one-two-four" 

The code ended up being more complex than I expected, but I didn't see a simpler way to do it.

[jcheng5]

sep = "-" should be sep = ns.sep?

[wch]

Oops, fixed.

[jcheng5]

LGTM!