Prepare release 1.9.0

Author: fhofherr

CHANGELOG.md

@@ -1,8 +1,8 @@
 Changelog
 =========
 
-Unreleased
-----------
+v1.9.0
+------
 
 * Add support for setting load balancer values via cluster-wide defaults: `HCLOUD_LOAD_BALANCERS_LOCATION`, `HCLOUD_LOAD_BALANCERS_NETWORK_ZONE`, `HCLOUD_LOAD_BALANCERS_DISABLE_PRIVATE_INGRESS`, `HCLOUD_LOAD_BALANCERS_USE_PRIVATE_IP` (#125)
 * Fix: allow referencing certificates by name (#116)