minor #75 sync the changelog (xabbuh)

This PR was merged into the 3.0.x-dev branch.

Discussion
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sync the changelog

Commits
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11d3bec sync the changelog

Author: xabbuh

CHANGELOG.md

@@ -1,6 +1,18 @@
 CHANGELOG
 =========
 
+3.1.0
+-----
+
+* Introduce a new `Person` class.
+* Constructing a `State` object with an instance of any child class of `Actor`
+  other than `Agent` as the second argument is deprecated. Starting with `4.0`,
+  only instances of `Agent` will be accepted.
+* The `State::getActor()` method is deprecated and will be removed in `4.0`.
+  Use `State::getAgent()` instead.
+* Added a `StateDocumentsFilter` class that allows to draft filters for
+  `StateDocument` objects.
+
 3.0.0
 -----