[REFACTORING]Stop to use utility method for readability
Make `EPUB::Parser::OCF::CONTAINER_FILE` and other constants deprecated
[REFACTORING]Use existing list to repeate parse method
[REFACTORING]Extract method to extract dcmes from XML
Swap argument order of #extract_dcmes
Add a comment for id_map
Remove blank lines
Use #extract_dcmes for titles
[REFACTORING]Use #extract_dcmes for languages
[REFACTORING]Use #extract_dcmes for other DCMESs
[REFACTORING]Use #extract_method for rights
Remove unused #collect_dcmes
Generalize attribute writer
Extract method #extract_refinee from #parse_metadata
[REFACTORING]Use #extract_refinee for links
Use String#split(nil) instead of strip.split
Make EPUB::Publication::Package::Metadata::Link#rel a Set
Add note about Link#rel to README and CHANGELOG