Add info about 3.7.8 to CHANGELOG.md

Author: Bartosz Litwiniuk

CHANGELOG.md

@@ -1,5 +1,12 @@
 # Backtrace Android Release Notes
 
+## Version 3.7.8
+- Add integration tests
+- Move common http response processing method to helper class 
+- Remove unused code
+- Add abstraction to gson serialization
+- Improve example-app Main Activity to work in same way on different Android versions
+
 ## Version 3.7.7
 
 - Added a new attribute to native reports - `breadcrumbs.lastId`