Same result for s2t and t2s（already finished)

I added the `test/test_s2t_and_t2s.py` for #16 .
The test failed, and I create small one `test_same1989googlefr`.

I print the `self.multialign` during align.
`[(((0,), (0,)), 'BLEU'), (((2,), (4,)), 'GAPFILLER'), (((3,), (3,)), 'GAPFILLER')]`

It seems align crosses each other.
I traced it. ((2,), (4,)) is added in `gapfiller`.
```python3
736 if besttarget == (targetgap[0],):
737      self.addtoAlignments(pregap)
```

Can you solve it?