update changelog and readme

Author: roycaihw

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 Kubernetes API Version: v1.19.15
 
+- No changes. The same as `v19.15.0a1`.
+
+# v19.15.0a1
+
+Kubernetes API Version: v1.19.15
+
 ### Bug Fix
 - Type checking in `Client.serialize_body()` was made more restrictive and robust. ([kubernetes-client/python-base#241](https://github.com/kubernetes-client/python-base/pull/241), [@piglei](https://github.com/piglei))
 

README.md

@@ -88,7 +88,7 @@ supported versions of Kubernetes clusters.
 - [client 12.y.z](https://pypi.org/project/kubernetes/12.0.1/): Kubernetes 1.15 or below (+-), Kubernetes 1.16 (✓), Kubernetes 1.17 or above (+-)
 - [client 17.y.z](https://pypi.org/project/kubernetes/17.17.0/): Kubernetes 1.16 or below (+-), Kubernetes 1.17 (✓), Kubernetes 1.18 or above (+-)
 - [client 18.y.z](https://pypi.org/project/kubernetes/18.20.0/): Kubernetes 1.17 or below (+-), Kubernetes 1.18 (✓), Kubernetes 1.19 or above (+-)
-- [client 19.y.z](https://pypi.org/project/kubernetes/19.15.0a1/): Kubernetes 1.18 or below (+-), Kubernetes 1.19 (✓), Kubernetes 1.20 or above (+-)
+- [client 19.y.z](https://pypi.org/project/kubernetes/19.15.0b1/): Kubernetes 1.18 or below (+-), Kubernetes 1.19 (✓), Kubernetes 1.20 or above (+-)
 
 > See [here](#homogenizing-the-kubernetes-python-client-versions) for an explaination of why there is no v13-v16 release.