included -1/t^2 factor in MID4 output

[victorkemp]

Fix for issue #152

Matches MSC and is how you'd expect it to be.

Example from Mystran with this PR:

MAT2     ,  4000001, 1.1845+6, -1.815+5, 5.0146+5, -8.213+5, 5.0146+5, -1.815+5, 0.0000+0, +1000005
 +1000005,        ,        ,        , 0.0000+0

and the same PCOMP from MSC:

  MAT2       400000001  1.1845E+06 -1.8155E+05  5.0146E+05 -8.2137E+05  5.0146E+05 -1.8155E+05  0.0000E+00
            0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00
                     0  0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00  0.0000E+00