Allow user to select the daily API call limit in authors_georef()

[embruna]

authors_georef() currently has a hard-coded daily limit of 2500 google georeferencing API calls. Edit to allow users to choose their daily limit, with 2500 as the default.

[embruna]

This should do it.

authors_georef <- function(data,
  address_column = "address", max_daily=NULL) {

  options(ggmap = list(display_api_key = FALSE))
  if (!is.character(data$address)) {
    stop("Address columns are not characters,
    please change to characters and try again")

 if(!is.null(max_daily)) max_daily <- 2500
  }

Need to be sure and update throughout, including examples and vignette.