A high-performance, index-based data structure toolkit. Provides an arena
allocator (ElemPool) used to build a cache-friendly PieList
(doubly-linked list) and FibHeap (priority queue).
#To Do List for `pielist`
These are suggestions for improvements:
-pool.shrink_to_fit(): An advanced (and potentially unsafe if indices are held) method to reclaim unused memory from the end of the pool's vector.
-Add more comparative tests against `index_list`