Legand:
- not done
+ done
/ in progress

--------------------------------------------------

+ Parameterize priority_size as a class variable using a class factory or similar.
+ Make it work for min and max, not just min
+ node retrieval
	+ find itself
	+ unit test
+ Add arbitrary node deletion
+ find the smallest
- delete the smallest
+ find the largest
- delete the largest
- Make it optionally keep the n smallest (largest) values only (probably via a wrapper class)
+ Make it handle/not handle duplicates via existing class factory
+ Improve the unit testing: should check for binary tree and heap invariants
- cython?
- change recursive methods to iterative?  Recursion stack overflow is a possibility in the current code.  Of course, it likely would be in an iterative
	implementation too - just not as fast.  Also, function/method calls are slow in python - an iterative implementation might help performance
+ reverse_iterator
+ content_class
+ content_class unit tests
- merge find_min and find_max
- create find_min_all and find_max_all
- merge find and find_all
+ test unique code - duplicate code is tested now
+ test actual duplicates!