Added Changelog

CHANGELOG

+# Changelog
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [1.2.1] - 2019-10-17
+### Added
+- CHANGELOG
+
+## [1.2.0] - 2019-10-16
+### Added
+- Extensive documentation.
+- API user, key and url can also be set as static class property.
+### Changed
+- ItemBase() base class for handling a setup, package, device or asset (in general: an item)
+- GroupBase() base class for handling a selection of items.
+- Code for standalone usage is now in __main__.py
+
+## [1.1.0] - 2019-10-15
+### Added
+- Custom info-beamer API exceptions
+- Handle setups with Setups() class
+- Handle overall info-beamer account with Infobeamer() class
+
+## [1.0.0] - 2019-10-14
+### Added
+- Project structure.
+- Load user, key, url for API with CLI or system environment variables.
+- Connect to API.