Implement a heap-based priority queue

[mwermelinger]

A min/max-priority queue can be implemented with a min/max-heap. (Section 16.6 in the M269 book.)

In subfolder paddles:

• Create a file priority_queue.py with a docstring explaining the Priority Queue ADT.
• Write a class HeapMinPriorityQueue that implements a min-priority queue with a binary heap, represented as a Python list.
• The __init__ method has a parameter with the priority-item pairs to be added to the queue (the parameter is of type collections.abc.Iterable[tuple].
• The inspector methods are:
  • return the front of the queue (item and corresponding priority)
  • return the size of the queue
• The modifier methods are:
  • enqueue a given item with a given priority
  • dequeue the next item and its priority (lowest value of all priorities)
• Add a heapsort function to sorting.py.

In subfolder tests:

• Create a file test_priority_queue.py that tests the modifier methods.