run towncrier for 2.9 and add project info

Author: obestwalter

CHANGELOG.rst

@@ -1,18 +1,50 @@
 CHANGELOG
 =========
 
-**Note** since version 2.8 releases are organized around Github projects.
-To see all closed issues and merged pull requests, visit the project on Github:
+The most important changes for each release are kept in this changelog.
 
-2.9.x: https://github.com/tox-dev/tox/projects/11
-2.8.x: https://github.com/tox-dev/tox/projects/6
+If you want to know more details: since version 2.8 releases are organized as Github projects.
+To see all closed issues and merged pull requests, contained in a release, visit the projects
+on Github:
+
+- 2.9.x: https://github.com/tox-dev/tox/projects/11
+- 2.8.x: https://github.com/tox-dev/tox/projects/6
 
 ..
     Everything below here is generated by towncrier. Do not edit directly.
     See https://pypi.python.org/pypi/towncrier for more information.
 
 .. towncrier release notes start
 
+Tox 2.9.0 (2017-09-14)
+======================
+
+Features
+--------
+
+- ``tox --version`` now shows information about all registered plugins - by
+  :user:`obestwalter` (`#544 <https://github.com/tox-dev/tox/issues/544>`_)
+
+
+Bugfixes
+--------
+
+- ``skip_install`` overrides ``usedevelop`` (``usedevelop`` is an option to
+  choose the installation type if the package is installed and `skip_install`
+  determines if it should be installed at all) - by :user:`ferdonline` (`#571
+  <https://github.com/tox-dev/tox/issues/571>`_)
+
+
+Improved Documentation
+----------------------
+
+- add `towncrier <https://github.com/hawkowl/towncrier>`_ to allow adding
+  changelog entries with the pull requests without generating merge conflicts;
+  with this release notes are now grouped into four distinct collections:
+  `Features`, `Bugfixes`, `Improved Documentation` and `Deprecations and
+  Removals`. (`#614 <https://github.com/tox-dev/tox/issues/614>`_)
+
+
 2.8.1 (2017-09-04)
 ==================