Fix bugs

1. Fix program crashed when accessing nested table (table[key][key]).
2. Change getGlobal and printLuaRef to be inline functions.
Merge branch 'develop' of github.com:sKabYY/LuaBacc into develop
Add -Wall -Wextra to g++ and rewrite some code
Fix a bug and drop unnecessary "inline".
Add a class LuaState, a wrapper for lua_State.
Test LuaState