specialize C++ compiler in clang toolchain
fix missing spaces.
Update README.md; The URL of the mruby home-page is accessible.
Merge pull request #1740 from tmash06/fix_missing_spaces

fix missing spaces.
Merge pull request #1741 from suzukaze/update-readme

Update README.md; The URL of the mruby home-page is accessible.
Merge pull request #1739 from take-cheeze/clang_cxx

Specialize C++ compiler in clang toolchain.