Added comprehensive changelog

Author: Geolim4

CHANGELOG.md

@@ -0,0 +1,17 @@
+##7.0.0-alpha
+##### 18 october 2017
+- __Global__
+  - Added php7 type hint support. Strict type support is coming in next alphas
+  - Added changelog as requested by @rdecourtney in #517
+  - Added `phpFastCacheInstanceNotFoundException` exception
+- __Drivers__
+  - Added Riak driver
+  - Fixed wrong type hint returned by Predis
+- __Cache Manager__
+  - Added custom Instance ID feature as requested in #477
+- __Helpers__
+  - Modified ActOnAll helper behavior, this helper now returns an array of driver returns and does no longer implements `ExtendedCacheItemPoolInterface`
+
+##7.0.0-dev
+##### 01 october 2017
+- Initialized v7 development