#298 Add version to first level of ActivityStream feeds

http://activitystrea.ms/schema/1.0/tag
https://activitystrea.ms/specs/json/1.0/

See https://github.com/jasnell/activitystrea.ms/issues/34 --- Greetings, TL;DR; Please add key `version` at the same level of key `generator`. Possible values: ``` http://activitystrea.ms/schema/1.0/tag https://activitystrea.ms/specs/json/1.0/ ``` I've built a userscript that converts [JSON Feed](https://openuserjs.org/scripts/sjehuda/Newspaper) into an readable HTML. I'm adding support for [ActivityStreams](https://nu.federati.net/api/statuses/public_timeline.as). I can determine if a file is of JSON Feed by looking into `json_file.version`, but not so in GNU social (StatusNet) ActivityStream feeds, unless I look into key `generator`, but then again, some other software (Mastodon et al.) might choose or have a plugin to deploy ActivityStream and they could use a different key. Thank you, Schimon