Documentation for `demo_train.py`

[thomasahle]

I'm trying to run demo_train.py, but it's unclear how it works. If I add the --glove parameter, it complains that both sift and glove is active, since sift is apparently active by default. Can I disable that? I can add the --data_dir parameter, but it doesn't seem to be used by the script, since opt is never passed to the glove loader. It also seems that I need to run another script before demo_train.py to split the input in queries and answers, but I can't tell which one.