Update changelog in preparation for the 1.7.0 release. (google#1230)

* Update changelog in preparation for the 1.7.0 release.

* Address review comments

Author: mbarbella-chromium

CHANGELOG.md

@@ -1,6 +1,15 @@
 Change Log
 ==========
 
+## Version 1.7.0
+- Better crash type reporting on various UBSan issues.
+- Initial support for Honggfuzz.
+- Additional fixes in preparation for migration to Python 3.
+- Migrated off deprecated App Engine Memcache to Cloud MemoryStore for Redis.
+- Added libFuzzer fuzzing support for Android (using HWASan).
+- Automatically correct certain common mistakes in dictionaries.
+- Various bug fixes.
+
 ## Version 1.6.1
 - Various bug fixes.