build: try to get travis.yml to build on liunux and osx

.travis.yml

@@ -1,11 +1,19 @@
-sudo: required
-dist: trusty
+matrix:
+  include:
+    - os: linux
+      dist: trusty
+      sudo: required
+    - os: osx
+      osx_image: xcode7.2
 language: cpp
 compiler:
   - clang
   - gcc
 before_install:
-  - sudo apt-get -qq update
-  - sudo apt-get install -y groff
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update; fi
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew install groff; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get -qq update; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sudo apt-get install -y groff; fi
 script:
-  - ./build-linux-64.sh
+  - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then ./build-osx.sh; fi
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then ./build-linux-64.sh; fi