Notable changes
* Add GitHub!
* `get_activities()` supports issues and pull requests, including comments and reactions. It's currently based on notifications, so it's best effort, not comprehensive, and only includes recently active issues/PRs.
* `create()` and `preview_create()` support issues, comments, [stars](https://help.github.com/articles/about-stars), and [reactions](https://help.github.com/articles/about-conversations-on-github/#reacting-to-ideas-in-comments).
* Twitter:
* Prefer MP4 and other video/... content types to HLS (.m3u8) etc. [Background.](https://twittercommunity.com/t/retiring-mp4-video-output/66093)
* Prefer HTTPS URLs for media images.
* `get_activities()`: Support -prefixed usernames in `user_id`.
* Facebook:
* Support new [recurring aka multi-instance events](https://stackoverflow.com/questions/45131646/decoding-recurring-events-from-facebook-open-graph-api). `create()` and `preview_create()` now only support RSVPs to individual instances of multi-instance events, to match the Facebook API itself.
* Try harder to find original (full) sized photo URLs, specifically `_o.jpg` files instead of `_s.jpg`.
* `create()` bug fix for photo and image URLs with unicode characters.
* Fixed bug where `get_activities(user_id=...)` included the authenticated user's own recent photos, albums, and news publishes.
* Instagram:
* Extract more user (`author`) data from scraped profile pages.
* Fix home page feed scraping.
* microformats2, Atom:
* Add enclosures for image attachments.
* Bug fixes for rendering image, video, and audio attachments inside shares and attachments. De-dupe images.
* microformats2:
* Handle simple string-only author properties.
* Add `fetch_mf2` kwarg to `json_to_object()` for fetching additional pages over HTTP to determine authorship.
* Generate explicit blank `p-name` in HTML to prevent old flawed [implied p-name handling](http://microformats.org/wiki/microformats2-implied-properties) [#131](https://github.com/snarfed/granary/issues/131).
* Fix `share` verb handling in `activity_to_json()` and `activities_to_html()` [134](https://github.com/snarfed/granary/issues/134).
* Remember which content contains HTML, preserve newlines in it, and don't translate those newlines to `<br>`s ([130](https://github.com/snarfed/granary/issues/130)).
* Atom:
* Fix timezone bugs in `updated` and `published`.
* JSON Feed:
* Omit title from items if it's the same as the content. (Often caused by microformats2's implied `p-name` logic.)