Fix for Gherkin's localization

[demidovsursu]

I try to use .feature files with the language option and found 2 bugs.

1. In GSteps.h need use "type" not "keyword" because "keyword" contains localized word.
   std::string keyword = children["type"];
2. The function read_data in GUnit/Detail/FileUtils.h read chars from utf8 files.
   I fixed this bug using UnicodeUtilities_read_code_point_from_utf8_source from gherkin-c library.

extern "C" {
typedef struct Utf8Source Utf8Source;
long UnicodeUtilities_read_code_point_from_utf8_source(Utf8Source* utf8_source);
Utf8Source* FileUtf8Source_new(FILE* file);
unsigned char Utf8Source_read(Utf8Source* utf8_source);
void Utf8Source_delete(Utf8Source* utf8_source);
}

inline std::wstring read_file(const std::string &feature) {
  FILE* file = fopen(feature.c_str(), "rb");
  if (!file) {
    throw std::runtime_error("File \"" + feature + "\" not found!");
  }
  std::wstring r;
  Utf8Source* utf8_source = FileUtf8Source_new(file);
  for(;;) {
    long code = UnicodeUtilities_read_code_point_from_utf8_source(utf8_source);
    if (code == WEOF) break;
    r+=(wchar_t)code;
  }
  Utf8Source_delete(utf8_source);
  fclose(file);
  return r;
}