Question: when did heroes of the storm come out
[{'answer': 'June 2 , 2015', 'provenance': [{'wikipedia_id': '38687734', 'title': 'Heroes of the Storm', 'start_paragraph_id': 27, 'start_character': 671, 'end_paragraph_id': 27, 'end_character': 684, 'bleu_score': 1.0, 'section': 'Section::::Development.\n'}]}, {'provenance': [{'wikipedia_id': '38687734', 'title': 'Heroes of the Storm', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 716, 'bleu_score': 0.9315196407143821, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18390172353238098370}, 'section': 'Section::::Abstract.'}]}]