fix CI

Author: paulofaria

Diff for: .travis.yml

@@ -1,10 +1,8 @@
 os:
   - linux
-  - osx
 language: generic
 sudo: false
 dist: trusty
-osx_image: xcode8.3
 addons:
   apt:
     sources:

Diff for: circle.yml

@@ -1,3 +1,6 @@
+machine:
+  xcode:
+    version: 9.0
 dependencies:
   override:
     - eval "$(curl -sL http://sh.zewo.io/install-libdill.sh)"