Merge pull request #16 from hintjens/master

Removed use of deprecated zmsg_push
Merge pull request #18 from hintjens/master

Fixed compile warnings
Fixed segfault in curve_selftest function curve_server
Merge pull request #20 from xpahos/master

Fixed segfault in curve_selftest function curve_server
Problem: client can't bind to 9004 in selftest

Address is being freed by previous test cases. Properly, libcurve
should migrate to CZMQ v3 API.

Solution: use different port for each test case.