3.0.0-beta2

docs: Add README, UPGRADING, EXTENDING guides and code examples
refactor: Make DefaultSession and DefaultSessionFactory non-final
feat: Implement PSR-4 compliant modern sessionhandler

3.0.0-beta1

test: Add unit tests (with mocks) mimicking the integration tests (real IO)
test: Modernize test suite layout
chore: metadata
style: php-cs-fixer