Allow gzipped barcode whitelist file.

void Chromap::LoadBarcodeWhitelist() {

  double real_start_time = GetRealTime();

  int num_barcodes = 0;

  if (1) {

    gzFile barcode_whitelist_file = 

      gzopen(mapping_parameters_.barcode_whitelist_file_path.c_str(), "r"); 

    char barcode[256];

    while (gzgets(barcode_whitelist_file, barcode, sizeof(barcode)) != NULL) {

      size_t barcode_length = strlen(barcode);

      if (barcode[barcode_length - 1] == '\n') {

        barcode[barcode_length - 1] = '\0';

        --barcode_length;

      }

      if (barcode_length > 32) {

        ExitWithMessage("ERROR: barcode length is greater than 32!");

      }

      if (barcode_length != barcode_length_) {

        if (num_barcodes == 0) {

          ExitWithMessage(

              "ERROR: whitelist and input barcode lengths are not equal!");

        } else {

          ExitWithMessage(

              "ERROR: barcode lengths are not equal in the whitelist!");

        }

      }

      uint64_t barcode_key = GenerateSeedFromSequence(

          barcode, barcode_length, 0, barcode_length);

      int khash_return_code;

      khiter_t barcode_whitelist_lookup_table_iterator =

        kh_put(k64_seq, barcode_whitelist_lookup_table_, barcode_key,

            &khash_return_code);

      kh_value(barcode_whitelist_lookup_table_,

          barcode_whitelist_lookup_table_iterator) = 0;

      assert(khash_return_code != -1 && khash_return_code != 0);

      ++num_barcodes;

    }

    gzclose(barcode_whitelist_file);

  } else { 

    std::ifstream barcode_whitelist_file_stream(

        mapping_parameters_.barcode_whitelist_file_path);

    std::string barcode_whitelist_file_line;

      ++num_barcodes;

    }

    barcode_whitelist_file_stream.close();

  }

  std::cerr << "Loaded " << num_barcodes << " barcodes in "

            << GetRealTime() - real_start_time << "s.\n";

}