DEBIAN env variable is defined on the OS X host as well

.travis.yml

@@ -1,8 +1,6 @@
-#before_script:
-  # - "sh -e /etc/init.d/xvfb start"
 before_install:
   - "export DISPLAY=:99.0"
-  - "test $DEBIAN_FRONTEND && sh -e /etc/init.d/xvfb start"
+  - "test "Darwin" != `uname` && sh -e /etc/init.d/xvfb start"
     #- "sh -e travis-chromium-script.sh"
 script: "DISPLAY=:99.0 bundle exec rake core_spec"
 
@@ -16,7 +14,6 @@ env:
   - JASMINE_BROWSER=firefox
   #- JASMINE_BROWSER=chrome
   - JASMINE_BROWSER=phantomjs
-  - JASMINE_BROWSER=safari
 
 matrix:
   allow_failures:
@@ -24,7 +21,4 @@ matrix:
     - env: JASMINE_BROWSER=phantomjs
   include:
     - language: objective-c
-      env: JASMINE_BROWSER=safari
-  exclude:
-    - language: ruby
-      env: JASMINE_BROWSER=safari
+      env: JASMINE_BROWSER=safari