rATTAINS 1.0.0

Major changes

This major release stabilizes the data structure returned by the functions
calling the ATTAINS API. There might be some breaking changes due to changes
in some column names and nested structure of the data. Unless there are major
changes in the data returned by ATTAINS, my goal is for the current data column
names and structure to stay consistent from this release forward.

• all API functions use tibblify::tibblify() to converted nested lists to
  tibbles. This change will ensure functions return consistent data structures
  between web calls. Some functions may return slightly different data structures
  compared to previous package versions (fixes #25, #31).
• added the .unnest argument to most functions that return API results. It
  defaults to TRUE to preserve backwards compatibility. If FALSE, results will
  be returned in the nest structure provided by ATTAINS.

Internal changes

• remove dependency on tidyjson.
• remove dependency on janitor.
• update citation file to use bibentry().
• removes magrittr pipe import/export.
• remove the write_disk_path folder used by vcr in the test folder.