Configuraptor

Fix

* Updating an optional field to None via _update or normal attribute was ignored ([`b9b8cec`](https://github.com/trialandsuccess/configuraptor/commit/b9b8cecd5935b0d626bc614a6fa04c7dfb559b77))

Fix
* **beautify:** Minor tweaks and cleanup ([`fdfe1fe`](https://github.com/trialandsuccess/configuraptor/commit/fdfe1fe42f51d639076ff8515e90b86d84bcbd5b))

Feature
* **beautify:** Added the beautify decorator to automatically set a nice __repr__ and __str__ (since these don't inherit) ([`366a8b0`](https://github.com/trialandsuccess/configuraptor/commit/366a8b0cb8d80ae21a21073bf7f5a01389696af6))

Documentation
* **beautify:** Include an example for `beautify` ([`b51d8d5`](https://github.com/trialandsuccess/configuraptor/commit/b51d8d508d8e94b12f99346e674d5ac5d08ae4c3))

Fix
* Extracted `convert_key` to own function so it can be used elsewhere ([`d923802`](https://github.com/trialandsuccess/configuraptor/commit/d923802e7577f2075f5051a724b3ed9a8443b8ff))

Fix

* **mypy:** Proper return type for register_dumper decorated functions like asjson ([`77a96ce`](https://github.com/trialandsuccess/configuraptor/commit/77a96ce2a8fd019dc41c8f6ee7258f6b1343ddbc))

Fix

* Allow excluding internal variables from asdict/asjson/etc ([`35af912`](https://github.com/trialandsuccess/configuraptor/commit/35af912e1949e6d0754976817b348c9a339db439))