Add heap project dir, README.

data_structures/heap/README.md
	-Add dir for the heap project.
	-Add a placeholder README.
Add heap package dir structure.

data_structures/heap/heap/(__init__, heap).py
	-Add a Python package dir structure for the heap project.
	-Define a skeleton `Heap` class in the `heap` module.
Rename heap module to data_structure.

data_structures/heap/heap/(heap -> data_structure).py
	-Rename the `heap` module to `data_structure`, because it
	conflicted with the package name and disrupted absolute package
	imports.
Debug insert(), define __setitem__().

data_structures/heap/heap/data_structure.py
	-`parent_ind` wasn't getting reset inside the `insert()` loop;
	fix.
	-Add varargs to `insert()`, to ease bulk inserts.
	-Rename `__length__()` to `__len__()`.
Add unittest tests for heap.

data_structures/heap/heap/test/(__init__, test).py
	-Add a subpackage for `unittest` unit-tests.
	-Add main test module `test`, main test class.
	-Define `test_insert()`.
Define Heap.__str__().

data_structures/heap/heap/data_structure.py
	-Define `Heap.__str__()`.
Implement Heap.remove().

data_structures/heap/heap/data_structure.py
	-Define functional `remove()`.
Define unit-test for Heap.remove().

data_structures/heap/heap/test/test.py
	-Define `test_remove()`.
	-Currently broken due to a bug in `Heap.remove()` (which arises
	when the last item in a Heap is removed).
Fix last-item removal bug in Heap.remove().

data_structures/heap/heap/data_structure.py
	-`Heap.remove()` blew up when the last item in a heap was
	removed, due to an `IndexError` that stemmed from index-value
	swapping.
	-Fix with a conditional on the length of the `Heap`.
Define Heap.__eq__(), document insert(), remove().

data_structures/heap/heap/data_structure.py
	-Add docstrings to `Heap.insert()`, `Heap.remove()`.
	-Define `__eq__()`.
Add module/function docstrings.

data_structures/heap/heap/(data_structure, test/test).py
	-Add module/function -level docstrings where missing.
Add usage example to README.

data_structures/heap/README.md
	-Add a code-block demonstrating example usage of the `Heap`
	package.
Merge branch 'data_structures/heap' into develop

data_structures/heap/
	-Implement a heap data-structure as a Python package.