v0.3.3

NEW FEATURES

• New data source NOAA legacy API with ISD, daily, and ish data via function
  ncdc_legacy(). (#54)
• New function isd() to get ISD data from NOAA FTP server. (#76)
• ERDDAP gridded data sets added. Now tabledap datasets are accessible via
  erddap_table(), while gridded datasets are available via erddap_grid(). Helper
  function erddap_search() was modified to search for either tabledap or griddap
  datasets, and erddap_info() gets and prints summary information differently
  for tabledap and griddap datasets. (#63)

MINOR IMPROVEMENTS

• erddap_data() defunct, now as functions erddap_table() and erddap_grid(), uses new
  store parameter which takes a function, either disk(path, overwrite) to store
  on disk or memory() to store in R memory.
• assertthat library removed, replaced with stopifnot()