update CHANGELOG.md (#148)

* update CHANGELOG.md
* add some more detail to explain we will stop testing in travis-ci on java 7

Author: wangjoshuah

CHANGELOG.md

@@ -24,6 +24,8 @@ You can now use feature flags in the Java SDK. You can experiment on features an
 - Remove track with revenue as a parameter. Pass the revenue value as an event tag instead
   - `track(String, String, long)`
   - `track(String, String, Map<String, String>, long)`
+- We will no longer run all unit tests in travis-ci against Java 7. 
+  We will still continue to set `sourceCompatibility` and `targetCompatibility` to 1.6 so that we build for Java 6.
 
 ## 1.8.0