Problem: OSX build not enabled

Solution: Enable OSX build with DRAFT and latest libzmq

Author: kurdybacha

.travis.yml

@@ -39,6 +39,10 @@ matrix:
             - g++-7
       env:
         - MATRIX_EVAL="CC=gcc-7 && CXX=g++-7" ZMQ_VERSION=4.2.5 DRAFT=1
+    - os: osx
+      osx_image: xcode8
+      env:
+        - MATRIX_EVAL="brew install cmake gcc && CC=gcc-7 && CXX=g++-7" ZMQ_VERSION=4.2.5 DRAFT=1
 
 sudo: required