added 'format','tz' parameters to 'nanotime','format' and 'print'

[lsilvest]

No description provided.

[eddelbuettel]

Something is not right here. I'll try to hit you on Slack... Nobody home.

Sent a quick commit your way which is now part of the PR. Rest looks good.

[eddelbuettel]

Ie

R> .getTz <- function(x, tz) {
+     if (tz=="") {
+         if (!is.null(tzone <- attr(x, "tzone")))
+             tz <- tzone
+         else
+             tz <- getOption("nanotimeTz", default="UTC")
+     }
+     tz
+ }
R> .getTz(Sys.time())  # calling with missing, no default given
Error in .getTz(Sys.time()) (from nano.R!9170Nws#2) : argument "tz" is missing, with no default
R>