fixes #119 linear-model not correctly computing t-probs

there's things more elegant than clojure's treatment of keyword arguments...

was:

    => (:t-probs (linear-model [-1 1 3 0] [2 3 -1 0]))
    A 2x1 matrix
    -------------
    1.65e+00
    1.53e+00
is:

    => (:t-probs (linear-model [-1 1 3 0] [2 3 -1 0]))
    A 2x1 matrix
    -------------
    3.55e-01
    4.65e-01