restore a bits
nan,+inf,-inf
refactor with lua_Alloc

Lua/LuaJIT is provided to be embedded.
So working with C library instead of Lua API/C is not a good idea.
Rockspec to install msgpack module using luarocks

To install, use :
 sudo luarocks make rockspec/lua-msgpack-native-scm-1.rockspec
Merge pull request #4 from mtourne/master

Adding a rockspec file to install msgpack module using luarocks
Update README.md
Merge https://github.com/kengonakajima/lua-msgpack-native
morge