Based on https://github.com/zendframework/zend-diactoros/releases/tag/1.2.1 (commit fd1e34d7db83eee7265446570d197ed3858db8b5 in this repo)

Added
-----

- Nothing.

Deprecated
----------

- Nothing.

Removed
-------

- Nothing.

Fixed
-----

- [zendframework/zend-diactoros#101](https://github.com/zendframework/zend-diactoros/pull/101) fixes the
  `withHeader()` implementation to ensure that if the header existed previously
  but using a different casing strategy, the previous version will be removed
  in the cloned instance.
- [zendframework/zend-diactoros#103](https://github.com/zendframework/zend-diactoros/pull/103) fixes the
  constructor of `Response` to ensure that null status codes are not possible.
- [zendframework/zend-diactoros#99](https://github.com/zendframework/zend-diactoros/pull/99) fixes
  validation of header values submitted via request and response constructors as
  follows:
  - numeric (integer and float) values are now properly allowed (this solves
    some reported issues with setting Content-Length headers)
  - invalid header names (non-string values or empty strings) now raise an
    exception.
  - invalid individual header values (non-string, non-numeric) now raise an
    exception.