Add temporary fix for composer prefer-lowest issue

Author: sagikazarmark

.travis.yml

@@ -31,6 +31,8 @@ before_install:
     - travis_retry composer self-update
 
 install:
+    # To be removed when this issue will be resolved: https://github.com/composer/composer/issues/5355
+    - if [[ "$COMPOSER_FLAGS" == *"--prefer-lowest"* ]]; then travis_retry composer update --prefer-dist --no-interaction --prefer-stable --quiet; fi
     - travis_retry composer update ${COMPOSER_FLAGS} --prefer-dist --no-interaction
 
 script: