Further travis tweaks (#606)

Author: GrahamCampbell

.travis.yml

@@ -28,14 +28,14 @@ matrix:
       dist: trusty
   allow_failures:
     - php: nightly
-    - php: hhvm-3.18
 
 before_install:
   - if [[ "$WITH_COVERAGE" != "true" && "$TRAVIS_PHP_VERSION" != "hhvm-3.18" && "$TRAVIS_PHP_VERSION" != "nightly" && "$TRAVIS_PHP_VERSION" != "7.1" ]]; then phpenv config-rm xdebug.ini; fi
   - if [[ "$TRAVIS_PHP_VERSION" = "hhvm-3.18" || "$TRAVIS_PHP_VERSION" = "nightly" ]]; then sed -i '/^.*friendsofphp\/php-cs-fixer.*$/d' composer.json; fi
 
 install:
-  - travis_retry composer install --no-interaction --prefer-dist
+  - if [[ "$TRAVIS_PHP_VERSION" != "nightly" ]]; then travis_retry composer install; fi
+  - if [[ "$TRAVIS_PHP_VERSION" = "nightly" ]]; then travis_retry composer install --ignore-platform-reqs; fi
 
 script:
   - if [[ "$WITH_COVERAGE" == "true" ]]; then ./vendor/bin/phpunit --coverage-text; else composer test; fi