add conditional to only run unit tests on linux

Author: tbarlow12

.travis.yml

@@ -21,9 +21,9 @@ before_script:
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then export DISPLAY=:99.0; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sh -e /etc/init.d/xvfb start; fi
   - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then sleep 3; fi
-  - npm install
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then npm install; fi
 script:
-  - npm test
+  - if [[ "$TRAVIS_OS_NAME" == "linux" ]]; then npm test; fi
 
 before_deploy:
   - |