print matrix according to viterbi alignment like
          fs
     -------------
    e|x| | | |
    s| |x| | |
     | | | |x|
     | | |x| |
     -------------

def show_matrix(es, fs, t, a):
    '''
    print matrix according to viterbi alignment like
          fs
     -------------
    e|x| | | |
    s| |x| | |
     | | | |x|
     | | |x| |
     -------------
    '''

    max_a = viterbi_alignment(es, fs, t, a).items()
    m = len(es)
    n = len(fs)
    return matrix(m, n, max_a, es, fs)