Add cpprefjp, C++ Reference Site in Japanese

https://sites.google.com/site/cpprefjp/

cpprefjp is C++ reference for Japanese.  This site is written by many
C++ experts including C++ starndard committee members and updated lively.
References are based on latest C++ specification known as C++11
(ISO/IEC14882:2011).  And there are many samples to understand C++ and
C++ STL library quickly.
It's very helpful for Japanese C++ Programmers.
Merge pull request #254 from rhysd/add/cpprefjp

Add cpprefjp, C++ Reference Site in Japanese