2.5.0

• Upgrade Groovy dependency to 2.5.x, fixing bytecode compatibility issues with JDK11+ in certain situations (#205)
• Groovy metaprogramming enhancements to Thymeleaf objects is now done via extension modules. This has led to a slight improvement in performance: ~10% faster to complete the included benchmark project on JDK8, memory footprint remains unchanged.
• Fixed the fragment cache not being cleared when dispatching/forwarding to the error page (#189)
• Revamped the documentation website on https://ultraq.github.io/thymeleaf-layout-dialect/ (#204)
• Rolled the benchmark project into this repo so that performance testing can be done right next to the code (#192)
• Migrated unit tests from JUnit to Spock (#193)