v0.2.0

Major changes since 0.1.0:

• added blimp (#237)
• added qasper (#264)
• added asdiv (#244)
• added truthfulqa (#219)
• added gsm (#260)
• implemented description dict and deprecated provide_description (#226)
• new --check_integrity flag to run integrity unit tests at eval time (#290)
• positional arguments to evaluate and simple_evaluate are now deprecated
• _CITATION attribute on task modules (#292)
• lots of bug fixes and task fixes (always remember to report task versions for comparability!)