2020-03-27: Allow for daily and irregular time series using xts. Make these internal change available in the CRAN version, too. 
2018-01-31: Fixed bug in translation of legacy keys. 
2017-11-16: Fixed bug in get_dataset that prevented correct use of apikey. 
2017-11-16: Made get_dataset and get_time_series work when series of length 0 are returned.
