Add a README to least_squares_estimation.

algorithms/hash_algorithms/README.md
	-Add a brief description of how to execute each file, and what
	output to expect.

algorithms/least_squares_estimation/
(README.md, least_squares_estimation.png)
	-Add `least_squares_estimation.png`, the image generated by
	`demo.py`.
	-Add a README summarizing the contents of
	`least_squares_estimation/`: includes a link to the wikipedia
	article about the algorithm, and display
	`least_squares_estimation.png`.