Python-lenv

**Full Changelog**: https://github.com/pkeorley/python-lenv/compare/v0.3.0...v0.3.1
* Fixed a bug with getting a key by value instead of getting a key by a choice between a value and a key

**Full changelog**: https://github.com/pkeorley/python-lenv/compare/v0.2.0...v0.3.0
* Implemented the `Metadata` class.
* Implemented meta parameters `raise_when_not_found` and `filters`.
* Renamed the `Meta` class to `MetaEnvironmentVariablesLoader`.

**Full Changelog**: https://github.com/pkeorley/python-lenv/compare/v0.1.0...v0.2.0
* Implementation of the ability to configure the loading of environment variables into a class using the `metadata` class attribute
* Refactoring and implementation of various mechanisms for accessing environment variables

**Full Changelog**: https://github.com/pkeorley/python-lenv/commits/v0.1.0