Notable changes

• microformats2:
  • Interpret h-cite and u-quotation-of (experimental) as attachments, e.g. for quote tweets.
  • Convert audio and video properties to AS attachments.
• Twitter:
  • Linkify @-mentions and hashtags in preview_create().
  • Support creating quote tweets from attachments with Twitter URLs.
  • When converting quote tweets to AS, strip quoted tweet URL from end of text.
  • Raise ValueError when get_activities() is passed group_id='@search' but not search_query.
• Instagram:
  • Improve HTML scraping error handling.
  • Support multi-photo/video posts.
• Facebook:
  • Disable creating "interested" RSVPs, since Facebook's API doesn't allow it.
• Atom:
  • Support media enclosures for audio and video attachments.
• Source.get_activities(): start raising ValueError on bad argument values, notably invalid Facebook and Twitter ids and Instagram search queries.
• Fix rendering and linkifying content with Unicode high code points (ie above the 16-bit Basic Multilingual Plane), including some emoji, on "narrow" builds of Python 2 with --enable-unicode=ucs2, which is the default on Mac OS X, Windows, and older *nix.