ATIS data split (train,dev,test) issues

[kpe]

I noticed some issues with the data split in the ATIS dataset (see visualization of the label distributions here.):

• duplicated data samples - 397 (from 5871)
• no train data for 5 intent and 7 slot labels
• up to 20% of the labels present in the training dataset are not present at all in the dev or test datasets

I believe this could make the interpretation of model performance measures somewhat unreliable, and tried to build an alternative, more balanced
data split here.