CRAN Release 0.3-1

Minor changes

• cder now reexports readr::problems() so that users can review
  parsing issues without loading readr.
• cder now writes the downloaded data to a tempfile when problems are
  encountered so that the user can review reprocess using an alternate
  approach if needed.
• Version bump from 3.0 to allow resubmission to CRAN, since test failures were
  detected only after package had been published to CRAN.