Docstrings and formatting improvements (#2418)

* Fix spelling in docstrings

* Improve comments and formatting

* Update print statement to reflect doctest change

* improve phrasing and apply black

* Update rat_in_maze.py

    This method is recursive starting from (i, j) and going in one of four directions:
    up, down, left, right.
    If a path is found to destination it returns True otherwise it returns False.

Co-authored-by: Christian Clauss <cclauss@me.com>