add change.log for 2.2
+* 2.2.0.Beta1 (2017-06-05)
+ ** support redis luttece client
+ ** introduce asynchronous cache API (when using luttece)
+ ** introduce auto load (read through) and auto refresh features
+ ** add timeUnit attribute to @Cached and @CreateCache
+ ** some internal API refactor
* 2.1.5 (2017-05-08)
** fix issue #5 : exception occurs when invoking @Cached method in @PostConstruct method with Spring Boot
* 2.1.4 (2017-04-27)
