Add README, and functional chained_hash_table.

data_structures/chained_hash_table/chained_hash_table.py
	-Add a module which defines `ChainedHashTable`, a functional
	chained hash table implementation.
Add docstrings to chained_hash_table module.

data_structures/chained_hash_table/chained_hash_table.py
	-Add docstrings to file header, `ChainedHashTable`, and all
	`ChainedHashTable` functions.
Add unittest tests; add items to constructor.

data_structures/chained_hash_table/chained_hash_table.py
	-Add an optional `items` argument to `__init__()`.

data_structures/chained_hash_table/test.py
	-Add `unittest` unit-tests for `insert()` and `remove()`.
Add docstrings to test, more tests.

data_structures/chained_hash_table/test.py
	-Define unit-tests for `contains()` and `load_balance()`.
	-Add docstrings to module header and all functions.
Add more content to chained_hash_table README.

data_structures/chained_hash_table/README.md
	-Add link to chained hash table literature.
	-Add module example usage (instantiation, function calls, etc.)
Increase unittest verbosity level, fix docstrings.

data_structures/chained_hash_table/test.py
	-Move the beginning of each function docstring onto the
	preceding line (which contains `"""`), to be properly printed by
	`unittest`.
Merge branch 'data_structures/chained_hash_table' into develop

data_structures/chained_hash_table/
	-Implement a chained hash table.