Log Message:
(security/R-argon2) Updated 0.2.0 to 0.4.0

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.