travis: try testing on osx as well
diff --git a/.travis.yml b/.travis.yml
index 4f5cca8..947b08d 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,6 +2,9 @@
 compiler:
   - clang
   - gcc
+os:
+ - linux
+ - osx
 script:
  - autoreconf -fiv
  - ./configure