Cleaned up XFAIL on resources

- this failing test was confusing users
- ZMTP v3.0 now does not define resources at all
- resources, along with other unimplemented aspects moved to
  RFC 37 ZMTP v3.1
Removed duplicate zmq_z85_* methods from zmq.h

Fixes #967
Merge pull request #968 from hintjens/master

Fixed issue #967