Build only vX.Y.Z tags, only from release branches (census-instrumentation#413)

Author: c24t

.circleci/config.yml

@@ -44,6 +44,7 @@ jobs:
 
 deployment:
   tag_build_for_cci2:
-    tag: /(([a-z]+)-)*([0-9]+)\.([0-9]+)\.([0-9]+)/
+    branch: /v([0-9]+)\.([0-9]+)\.([0-9]+)/
+    tag: /v([0-9]+)\.([0-9]+)\.([0-9]+)/
     commands:
       - true