Support Symfony 5

[vincentchalamon]

• Update tests for supported versions of Symfony (3.4, 4.4, 5.0)
• Update tests for supported versions of PHP (7.2, 7.3, 7.4)
• Upgrade Travis configuration
• Update PHPUnit version
• Add and apply php-cs-fixer

CI: https://travis-ci.org/github/misd-service-development/phone-number-bundle/builds/678087460

:warning: Regression detected in giggsey/libphonenumber-for-php:^8.10.1: https://github.com/giggsey/libphonenumber-for-php/issues/376

[vincentchalamon]

Closing in favor of https://github.com/odolbeau/phone-number-bundle