Install without platform deps for initial install

Author: weierophinney

.travis.yml

@@ -69,7 +69,7 @@ before_install:
   - composer self-update
 
 install:
-  - travis_retry composer install $COMPOSER_ARGS
+  - travis_retry composer install $COMPOSER_ARGS --ignore-platform-reqs
   - if [[ $TRAVIS_PHP_VERSION =~ ^5.6 ]]; then travis_retry composer update $COMPOSER_ARGS --with-dependencies $LEGACY_DEPS ; fi
   - if [[ $DEPS == 'latest' ]]; then travis_retry composer require --dev --no-update $COMPOSER_ARGS $LATEST_DEPS ; fi
   - if [[ $DEPS == 'latest' ]]; then travis_retry composer update $COMPOSER_ARGS ; fi