Created by: wangkuiyi

For example:

std::string s = string::Sprintf("%2.2f", 12.3456);
string::Printf("%2.2f", 12.3456);
string::Fprintf(std::cerr, "%2.2f", 12.3456);

This implementation depends on a simplifcation and port of tinyformat.

The motivations and comparisons are in the file comment of paddle/string/printf.h.