Include EPUB::Publication to TestMetadata
Add a test for extended title
Add tests for Fixed Layout
Add more tests for rendition:layout of metadata
Fix typos: Metata -> Metadata
Fix a typo: remoe -> remove
Fix typos: -= -> ==
Implement FixedLayout::MetadataMixin
Define MetadataMixin#make_reflowable and #make_pre_paginated
[REFACTORING]Redifine MetadataMixin#reflowable and #pre_paginated by .define_method
Define setter utility methods
[REFACTORING]Resuse converted method name