Add test for no translation/alignment score

Author: isaac091

tests/corpora/test_aligned_word_pair.py

@@ -10,6 +10,10 @@ def test_parse():
     assert len(wps) == 1
     assert wps[0].translation_score == 0.111111
     assert wps[0].alignment_score == -1
+    wps = list(AlignedWordPair.from_string("1-0"))
+    assert len(wps) == 1
+    assert wps[0].translation_score == -1
+    assert wps[0].alignment_score == -1
 
 
 def test_parse_to_string():