Extract Twitter/FB embeds

[tarunima]

At present, only images, videos and texts from a post are extracted and stored in a dictionary for a post. Thus only these media types are indexed and searchable.
Twitter and FB embeds need to be parsed. Since the html elements for each site are different, this task could be subdivided into sub tasks for each of the running scrapers: https://github.com/tattle-made/tattle-research/blob/master/factchecking_sites_status.md