use travis_retry on composer require/install

Author: michaeldyrynda

.travis.yml

@@ -25,13 +25,11 @@ matrix:
     - php: 7.2
       env: ILLUMINATE_VERSION=5.6.*
 
-before_install:
-  - composer require "illuminate/database:${ILLUMINATE_VERSION}" --no-update -v
-  - composer require "illuminate/events:${ILLUMINATE_VERSION}" --no-update -v
+before_install: travis_retry composer require "illuminate/database:${ILLUMINATE_VERSION}" "illuminate/events:${ILLUMINATE_VERSION}" --no-update -v
 
 install: composer update --prefer-source --no-interaction --dev -v
 
-script: vendor/bin/phpunit --debug -c phpunit.xml --coverage-clover=coverage.clover
+install: travis_retry composer install --prefer-dist --no-interaction --no-suggest -v
 
 after_script:
     - wget https://scrutinizer-ci.com/ocular.phar