Add command option to print align scores

[h-j-han]

This PR is slight augmentation of adding command option to append forward and backward align scores on the alignment pairs.
(It's similar with #44 but more non-intrusive way :) , just modifying one python file. )

For examples,

• Basic usage

$ python force_align.py fwd_params fwd_err rev_params rev_err
0-0 1-1 2-1 2-2 3-3 4-2 5-4 6-5 6-7 7-6 8-5
0-0 1-1 2-2 3-2 3-3 4-4 5-5 5-6 6-7 6-9 7-8 8-9 9-10
0-0 0-1 1-3 2-4 3-5

• Added command option append forward and backward score separated with tabs.

$ python force_align.py fwd_params fwd_err rev_params rev_err grow-diag-final-and fwdbwd
0-0 1-1 2-1 2-2 3-3 4-2 5-4 6-5 6-7 7-6 8-5     -45.1583        -75.626
0-0 1-1 2-2 3-2 3-3 4-4 5-5 5-6 6-7 6-9 7-8 8-9 9-10    -68.421 -71.7015
0-0 0-1 1-3 2-4 3-5     -37.883 -14.6208