[GH-100] feature/add-timestamped-speaker-turns

[tohuynh]

Add timestamped-speaker-turns to transcript format. Resolves #100

• Modified SeattleEventScraper to scrape for closed caption file URI

• Added a new module WebVTTSRModel that implements SRModel that takes the closed caption file URI and produces transcripts in three formats: raw, timestamped-sentences, and timestamped-speaker-turns

• Modified EventGatherPipeline to use a mixture of speech recognition models. That is, if there is a closed caption file URI, use WebVTTSRModel to produce transcripts. Else, use GoogleCloudSRModel to produce transcripts.

Tests

• Added a few fake files(fake_caption.vtt, fake_timestamped_sentences.json) to test WebVTTSRModel

• Test EventGatherPipeline new mixture of speech recognition models. That is, test for when WebVTTSRModel failed and succeeded in producing transcripts.

• Added an example_transcript_speaker_turns.json to be consistent with other example_transcripts.json

[tohuynh]

New changes has those changes you requested.