rework xml:dom configurations and pull base mappings out of converter classes
explicitly require parse_queue in converter.rb
require jsonmodel in jsonmodel_wrap
require asutitls in parse_queue.rb
lets DOM converters work with document fragments

squash me
add tests for possible namespace configurations of marcxml docs
support subclassing and reconfiguring of xml converters
remove comments and puts
update lcnaf converter to use new config method
add saxerator dependency
bump saxerator
bump saxerator again
throw out nokogiri reader and use saxerator