comtradr 1.0.6

Minor improvements

• Replaced the poorman dependency (scheduled for archival on CRAN) with
  dplyr. This does not add any new transitive dependencies, as all of
  dplyr's dependencies were already required through other imports.

Bug fixes

• ct_get_bulk() now validates the frequency argument instead of failing
  with an obscure object 'date_range' not found error.
• Invalid partner / partner_2 values now produce a readable error message
  that lists each invalid code once, instead of repeating the message for
  every code.
• ct_migrate_cache() no longer fails with argument "message" is missing
  when reporting a failed copy.
• Fixed HTTP 414 "URI Too Long" errors when querying long code lists, e.g.
  partner = "all_countries" (#103). The Comtrade API rejects URLs longer
  than about 2000 characters. ct_get_data() now detects
  this before performing the request, transparently splits the partner and/or
  reporter codes into multiple requests and combines the results into a
  single data.frame. With process = FALSE splitting is not possible (a
  single response object is returned) and a warning is issued instead.