Update .travis.yml

test/slow/locale/176.php depends on this locale being present

.travis.yml

@@ -4,6 +4,6 @@ compiler:
 before_script: 
   - ./configure_ubuntu_12.04.sh
 # for some tests  
-  - sudo locale-gen de_DE
+  - sudo locale-gen de_DE && sudo locale-gen zh_CN.utf8
   - HPHP_HOME=`pwd` make -j 8
 script: hphp/hhvm/hhvm hphp/test/run --arg --threads 2 quick zend slow