C++特性

1. Multiple inheritance: http://www.learncpp.com/cpp-tutorial/117-multiple-inheritance/

2. Virtual Base Class: http://www.learncpp.com/cpp-tutorial/118-virtual-base-classes/

3. Pointers and References to Base Class of Derived Objects: http://www.learncpp.com/cpp-tutorial/121-pointers-and-references-to-the-base-class-of-derived-objects/

4.如何实现一个不能被继承的类：http://www.parashift.com/c++-faq/final-classes.html