WordNet data path is parsed incorrectly on Windows

[Ulenspiegel]

On Windows, the library only recognizes WordNet data residing in directories named .\data*. That's because file filtering in wnram.New() is done using 'path.Base(), which doesn't handle backslash directory path separators properly:

		if strings.HasPrefix(path.Base(filename), ".") || strings.HasSuffix(filename, "~") || strings.HasSuffix(filename, "#") {
			return nil
		}
		// read only data files
		if !strings.HasPrefix(path.Base(filename), "data") {
			return nil
		}

Think both cases should be replaced with the cross-platform filepath.Base() to work correctly.