master (Release Candidate for v0.2.0)

* Begin FederateAPI unofficial implementation report.
* All 'vocab.Object' types and types extending from 'vocab.Object' now have an
      'IsPublic' method that will return true if the 'to', 'bto', 'cc', or 'bcc'
      properties have the ActivityPub special Public collection IRI.
* Use 'OrderedCollection' as the default type for 'likes', 'liked',
      'following', and 'followers' properties if the actor or object does not
      have an IRI, 'Collection', or 'OrderedCollection' set for these
      properties.
* Examine the IRI of 'objects' when applying the Origin Check policy for Update
      and Delete activities.
* If a federated Activity was already received, do not execute its side effects
      a second time.
* Add 'Like' activities to the 'likes' collection, instead of adding the
      actors. This was a specification-violating behavior.
* No longer try to fetch IRIs when deduping by IRI.
* Remove unused methods from fed_test.go.
* Fix Media Type header detection for ActivityPub messages.
* Improve code generation to remove 230,000 lines of code from the vocab
      package.
* Add list of contributors to CONTRIBUTING.md.
* README examples are tagged with golang syntax highlighting.

v0.1.1 2018-06-13

* Begin SocialAPI unofficial implementation report.
* Improved HTTP header detection for ActivityPub requests.
* Activities added to outboxes are now Set (in addition to the outbox itself).
* Fixed panic where the 'bcc' and 'bto' properties were improperly guarded.
* Fixed authn/authz shadowing when serving ActivityStream objects, causing only
      HTTP Signatures to be enforced.
* Under certain circumstances, IRIs will be fetched when an Add Activity is
      received. This behavior is a stepping stone towards a comprehensive
      solution in a future patch.
* SocialAPI Undo Activity has actors enforced the same way as the FederatedAPI.
* IRI normalization: Objects, Activities, and Links will no longer be duplicated
      when added to Collection types. Instead, IRIs are added.
* Serving ActivityStream objects will now remove the 'bcc' and 'bto' properties.
* Serving a Tombstone ActivityStream response now uses the HTTP 410 Gone status
      code.
* The 'vocab' and 'streams' subpackages now generate code to multiple files
      instead of a single large one.
* The 'deliverer' subpackage now has test coverage.

v0.1.0 2018-05-30

* Initial release of the 'deliverer' subpackage.
* Initial release of the 'pub' subpackage.
* Initial release of the 'streams' subpackage.
* Initial release of the 'tools' subpackage.
* Initial release of the 'vocab' subpackage.
* Support for ActivityStream static types in Go.
* Support for ActivityStream serialization and deserialization.
* Support for ActivityPub POST and GET to actor inboxes.
* Support for ActivityPub POST and GET to actor outboxes.
* Support for SocialAPI, FederatedAPI, or both for inbox and outboxes.
* Support for ActivityPub GET to fetch ActivityStreams.
* Support for HTTP Signature verification.
* Support for basic SocialAPI Activity behaviors.
* Support for basic FederatedAPI Activity behaviors.
* Support for Application-customized authn/authz behaviors.
* Support for Tombstone for Delete Activities.
* Test 'vocab' against examples in the spec.
* Test 'streams' against the test repository.
* Test 'pub' with over >100 end-to-end black box tests.