Param

* Added 'allow_None' support to all Parameters. Any subclass of
Parameter that checks types and/or values should be modified to add
appropriate handling of allow_None.
* Improved pretty printing (script_repr) of Parameterized instances,
and made available via the pprint method. The script_repr name will
be removed in a future release.
* Added (reproducible) time-dependent random streams
(numbergen.TimeAwareRandomState).
* Added label and unit parameters to param.Time class.
* Improved optional IPython extension.

A full list of changes since the previous release is available
[on GitHub](https://github.com/holoviz/param/compare/v1.2.1...v1.3.0).

* Minor bugfix release to fix issues with version when param is
installed in a foreign git repository
* Made version module optional
* Improved ClassSelector and ParamOverrides

A full list of changes since the previous release is available
[on GitHub](https://github.com/holoviz/param/compare/v1.2.0...v1.2.1).

* Added support for Python 3 (thanks to Marco Elver).
* Dropped support for Python 2.5.
* Added version module.
* Added optional numbergen package.

A full list of changes since the previous release is available
[on GitHub](https://github.com/holoviz/param/compare/v1.1.0...v1.2.0).

* Switched to Python's own logging module.
* Improved support for time when using Dynamic parameters.
* Optional extension for IPython users.

A full list of changes since the previous release is available
[on GitHub](https://github.com/holoviz/param/compare/v1.0.0...v1.1.0).

* First standalone release.

Pre-1.0 (2003)

* Param was originally developed as part of [Topographica](http://ioam.github.io/topographica/), and has been in heavy usage as part of that project since 2003.