v3.0

PR #52

• [BC break] Dropped support for PHP 5.x. PHP 7.1 minimum required.
• Added a new HTMLPurifierConfigFactory to handle cache properly and to build custom html definition from bundle semantic configuration.
• [BC Break] The bundle configuration has changed
• Added CHANGELOG file
• Refactored SerializerCacheWarmer to preload each profile configuration
• [BC break] Added type hints and return type hints