Initializing utf8 encoded string c++11

I have a problem initializing utf-8 encoded string. I am using Visual Studio 2013.

#include <string>
#include <iostream>

using namespace std::string_literals; // enables s-suffix for std::string         literals

int main()
{

string S1 = u8"hello"; // std::string

}

Error   1   error C2039: 'string_literals' : is not a member of 'std'                   c:\users\veroonika\documents\visual studio 2013\projects\string literals test u8 string\string literals test u8 string\source.cpp   5   1   string literals test u8 string
Error   2   error C2871: 'string_literals' : a namespace with this name does not exist  c:\users\veroonika\documents\visual studio 2013\projects\string literals test u8 string\string literals test u8 string\source.cpp   5   1   string literals test u8 string

Why does compiler not recognize the namespace?