Initialized project: composer, phpunit, gitignore.
Added test MetassioneTest. Added test stubs: POPOObjectFillerTest, POPOConverterTest
Fixed paths in composer.json
POPOConverter - usage for: empty object, array of empty objects, invalid values
Fixed paths and namespaces for test files
POPOConverter - usage for: objects with simple typed properties
POPOConverter - usage for: simple types, arrays
POPOConverter - usage for: complex object hierarchy