Log Message:
Update to 2.2. From the changelog:

- nullmailer-send no longer generates bounces for rejected bounces.
  Thanks Fejes József

- Fixed compile error in sendmail on GCC older than 4.9.

- Fixed treating authentication failure as message rejection.
  Thanks Fejes József

- nullmailer-inject now sets the full name of the sender to the user
  name as a fallback. This helps distinguish system sent messages when
  the MTA rewrites the address (as does GMail, for example).

- Fixed compatibility issue with gnutls 3.6 (and possibly others).