Release 0.4-0:
  * Update argon2 internals to release 20190702.

Release 0.3-0:
  * Changed argument "type" to "variant" in pw_hash().
  * Expose argon2 secondary inputs to users.
  * Fixed a bad error message.

Release 0.2-0:
  * Added Wikipedia link to DESCRIPTION.
  * Fixed several memory errors flagged by Valgrind.
  * Renamed raw_to_char() to raw_as_char().

Release 0.1-0:
  * Added pw_hash() and pw_check()
  * Added blake2b()
  * Added raw_to_char()
  * Added gen_nonce()
