Change lexical alignment default to 1-grams

[fusaroli]

No article in the current literature uses n-grams above 1 for lexical alignment. It'd make sense to change the default to 1.

[fusaroli]

The fix seems pretty straightforward: in the calculate alignment.py, function LexicalPOSAlignment, the line
for ngram in range(2,maxngram+1):

should become

for ngram in range(1,maxngram+1):

This however has the potential drawback of providing the user with an additional meaningless syntactic alignment of 1-grams.
No biggie for me, but if we want to avoid that, it could be solved by not passing along the penn_tok1 and penn_lem1 (including the stan stuff).