PyPE solution to PE problem 83

    ProjectEuler.net problem 83
    ===========================

    NOTE: This problem is a significantly more challenging version of Problem 81.

    In the 5 by 5 matrix below, the minimal path sum from the top left to the
    bottom right, by moving left, right, up, and down, is indicated in bold red
    and is equal to 2297.

        131 673 234 103 18
        201 96 342 965 150
        630 803 746 422 111
        537 699 497 121 956
        805 732 524 37 331

    Find the minimal path sum, in matrix.txt (right click and 'Save Link/Target
    As...'), a 31K text file containing a 80 by 80 matrix, from the top left to
    the bottom right by moving left, right, up, and down.

    Solution
    --------

    Note that an efficient algorithm for solving this has already been developed
    for problem 82. Please refer to PyPE.solutions.pype_082 for a description of
    the solution algorithm.

    We simply modify the starting parameters (i.e. filename, starting/ending
    nodes, and edges).

    Answer
    ------

    425185