markovvis - a simple interactive visualiser for time-homogeneous markov chains

Basic instructions:
    Holding down space progresses time (rate adjustable with '+' and '-'); the
    dimension of the system can be adjusted with '1' and '2'; both mouse
    buttons do things, and right-clicking and dragging does something special
    in the initial mode. Clicking with both mouse buttons simultaneously on a
    matrix entry lets you type in a new value. 'g' and 's' switch between
    modes. No simple way to read a matrix from a file or anything, but state.h
    is the file to hack if you want to hardcode something.
