Anytree

* Clarify detach/attach usage (28)
* Fix inconsistent tree structure visible in detach/attach methods (29)
* Implement AnyNode class
* Add importer/exporter structure
* Implement DictImporter
* Implement DictExporter
* Implement JsonImporter
* Implement JsonExporter
* Move RenderTreeGraph to DotExporter, keeping legacy
* Fix documentation conflict with 2.2.2
* Fix external documentation links
* Fix python 3.6 warning
* Add read-only trick
* Improve Documentation

* Add support for undirected graphs 26
* Fix issue in Attach/Detach Protocol 29
* Fix node kwargs issue 24
* Fix documentation 22

- Clarify .anchestors typo
- Try to fix 3.4 install issue.

* Add possibility to set children directly
* Fix issue in Iterators

* Fix typos
* Add package meta data.

- add `RenderTree().by_attr()`
- Implment `ZigZagGroupIter()`
- fix documentation
- refactor