Add qa skang

[sunnnymskang]

Processing Bigbio QA dataset to Machamp classification and sequence type.
In detail,

1. All Bigbio QA dataset has been converted to classification formatting

• yesno qa: directly converted to classification in the following format "text": context +' ' + [SEP]+ ' '+ Question / 'labels' : yes/no
• multiple choice qa (MCQA) in the following format: "text": context +' ' + [SEP]+ ' '+ Question + "Answer is ' + Answer / 'labels': yes/no
• Each choice in MCQA has been converted to data points (i.e. if MCQA has 4 choices, then four classification Machamp data was created

2. For those MCQA dataset that has exact match between answer and prompt has been converted to MaChamp sequence type

• format: 'sequence': tokenized (context + question) /'labels': ans/none