Fix bugs in msr_sqa dataset
The last version has many problems,

1) Errors in table load-in. Split by a single comma instead of using pandas is wrong.
2) id reduplicated in _generate_examples function.
3) Missing information of history questions which make it hard to use.

I fix it refer to https://github.com/HKUNLP/UnifiedSKG. And we test it to perform normally.