Merging zendframework/zendframework#5942

Merge branch 'hotfix/5942' into develop

* hotfix/5942:
  [zendframework/zendframework#5942] skip some tests when ext/intl is not present
  Use --prefer-source flag for composer
  [zendframework/zendframework#5942] Ensure TranslatorServiceFactory remains BC with < 2.3.0

.travis.yml

@@ -9,7 +9,7 @@ php:
 
 install:
   - sudo apt-get install parallel
-  - composer install --dev
+  - composer install --dev --prefer-source
 
 before_script:
   - mkdir -p build/coverage