Increase travis composer update mem limit

Author: torreytsui

.travis.yml

@@ -58,7 +58,7 @@ before_install:
   - if [ "$SYMFONY_VERSION" != "" ]; then composer require symfony/symfony:${SYMFONY_VERSION} --no-update; fi
   - export BRANCH=$(if [ "$TRAVIS_PULL_REQUEST" == "false" ]; then echo $TRAVIS_BRANCH; else echo $TRAVIS_PULL_REQUEST_BRANCH; fi)
 
-install: travis_wait composer update --prefer-dist $COMPOSER_FLAGS
+install: travis_wait php -d memory_limit=3G composer update --prefer-dist $COMPOSER_FLAGS
 
 script:
   - if [ "${TEST_INSTALLATION}" == true ]; then make test_installation; else make test; fi