0.2.1

New datasets:

• ELI5
• CompGuessWhat?!
• BookCorpus
• Piaf
• Allociné
• BlendedSkillTalk

New features:

• .filter method
• option to do batching for metrics
• make datasets deterministic

New commands:

• nlp-cli upload_dataset
• nlp-cli upload_metric
• nlp-cli s3_datasets {ls,rm}
• nlp-cli s3_metrics {ls,rm}