Prepared changelog for the approaching V3

Author: Geolim4

CHANGELOG.md

@@ -1,2 +1,15 @@
 ## 3.0.0
-##### xx xxxx 2018
+##### 1 june 2018
+
+- Added Symfony 4 (Flex) compatibility (thanks to @Pastisd)
+- Updated Phpfastcache service which is now private, use Symfony [D.I](https://symfony.com/doc/current/components/dependency_injection.html) instead.
+- Updated Phpfastcache dependency to the v7
+- Updated namespace for more consistency and to comply with moderns standards
+- Improved DataCollector interface by retrieving more information about cache
+- Improved Opcache efficiency, thanks to PHP7
+- Added deep tests (unit. + func.) to ensure you that the bundle is well-tested
+- Added CRUD-like commands, check out [README.md](./README.md#computer-cli-command-interactions)
+- Added "Cacheable Response" feature, check out [README.md](./README.md#bulb-introducing-cacheable-responses-v3-only)
+- Performed global code review to remove code aberrations and simplify portions of code.
+- Migration guide available [here](./src/Resources/Docs/migration/MigratingFromV2ToV3.md) to migrate from the Phpfastcache Bundle v2.
+