deque

[redorav]

• Add erase function
• Only allow POT chunk sizes - rework division to be &
• Add a reserve() function. We can avoid a lot of reallocations if we know our size upfront. Due to the way our deque works, we can allocate all the chunk upfront and avoid all the expensive checking and resizing during push_back
• Add a more efficient starting point. If we know that we're going to be doing many push_backs, push_fronts or a balanced approach, we can try to rebalance the chunks to avoid moving them around so much