Fixed various memory leaks
Renamed zpipes_msg_dump -> _print
Cosmetic fixes
Added selftest script
Update pkg-config file

remove deps on zmq, zyre, czmq, link to new client lib rather
than old.
Use CZMQ zsys_run_as ()

Needs latest CZMQ master.
Switch to using abstract IPC endpoints
Problem: handshake killed 3rd innocent node

When a node received a "HAVE WRITER" and then "HAVE READER" from
the cluster, it would falsely try to become a pipe writer. This
caused an assertion failure on zpipes_server.c:262 as the code
caught this impossible situation.

Solution: when seeing two peers handshake the same pipe, drop the
pipe entirely.

Fixes #82.

Note: I didn't set up a reproducible test case so I'm not 100%
sure the fix is accurate.
Unpinned Zyre version
Merge pull request #80 from hintjens/master

Various small fixes