Demo implementation of c++ forward list

Todo's:

1. add find
2. add sort
3. Copy constructor, swap, destructor
4. Make iterator more robust

#Reference

1. Apache list implementation
2. Stanford list implementation
3. VC++ list implementation

1. Custom Iterators: https://web.stanford.edu/class/cs107l/handouts/04-Custom-Iterators.pdf
2. Custom Containers: https://stackoverflow.com/questions/7758580/writing-your-own-stl-container
3. Custom Allocators: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2486.pdf
4. Apache list (doubly linked list): https://github.com/apache/stdcxx/blob/trunk/include/list