Refactored Cnab240::Arquivo::Arquivo specs
Added debugger gem as a development dependency
The following methods now expect an instance of IO (e.g. an instance of File):
  Cnab240::Arquivo::Arquivo#save_to_file
  Cnab240::Arquivo::Arquivo.load_from_file
  Cnab240::Builder#load_from_file
  Cnab240::PagamentoBb#save_to_file
  Cnab240::PagamentoBradesco#save_to_file
  Cnab240::PagamentoItau#save_to_file
  Cnab240::PagamentoSicoob#save_to_file

The gem version was raised to 0.0.20