[travis-ci] Composer install --ignore-platform-reqs

Remove platform constraint requirements when install. Tests already skip the execution if the required plafform requirement is not present

Author: Maks3w

.travis.yml

@@ -24,7 +24,7 @@ before_install:
   - if [[ $EXECUTE_TEST_COVERALLS != 'true' ]]; then phpenv config-rm xdebug.ini || return 0 ; fi
 
 install:
-  - travis_retry composer install --no-interaction --prefer-source
+  - travis_retry composer install --no-interaction --ignore-platform-reqs
 
 script:
   - if [[ $EXECUTE_TEST_COVERALLS == 'true' ]]; then ./vendor/bin/phpunit -c phpunit.xml.travis --coverage-clover clover.xml ; fi