Disable composer memory limit & Add PHP 7.4 tests

Author: dmitry-ivanov

.travis.yml

@@ -3,14 +3,15 @@ language: php
 php:
   - 7.2
   - 7.3
+  - 7.4
 
 cache:
   directories:
     - $HOME/.composer/cache
 
 install:
-  - travis_retry composer install --no-interaction --prefer-dist
-  - travis_retry composer require --no-interaction --prefer-dist --dev php-coveralls/php-coveralls
+  - COMPOSER_MEMORY_LIMIT=-1 travis_retry composer install --no-interaction --prefer-dist
+  - COMPOSER_MEMORY_LIMIT=-1 travis_retry composer require --no-interaction --prefer-dist --dev php-coveralls/php-coveralls
 
 script: vendor/bin/phpunit --verbose --coverage-clover build/logs/clover.xml