use RubyFacets
use RSS::Rss::Channel::Item as Class of a item of NDLSearch
add accessors of NDLSearch::RdfItem#title, creators, publishers, subjects, classifications, et al
refactoring: divide lib/ndl_search.rb into lib/ndl_search/*.rb
Merge branch 'use_rdf_data_for_import_bibliographic_records' into develop