update change log for 1.15.0 release (#92)

Author: dgrove-oss

core/python3Action/CHANGELOG.md

@@ -19,6 +19,12 @@
 
 # Python 3 OpenWhisk Runtime Container
 
+## 1.15.0
+  - Build proxy from 1.16.0 release of openwhisk-runtime-go
+  - Update to golang:1.15 and buster. (#90)
+  - Ambiguous name changed to python3ActionLoop (#89)
+  - Updated Python runtimes to use "Action Loop" Proxy with new async handshake (#82)
+
 ## 1.14.0
   - Update base image to openwhisk/dockerskeleton:1.14.0
   - Support for __OW_ACTION_VERSION (openwhisk/4761)