Merge pull request #31 from stanley-cheung/master

Bump to version 1.52.0

Author: stanley-cheung

composer.json

@@ -5,7 +5,7 @@
   "keywords": ["rpc"],
   "homepage": "https://grpc.io",
   "license": "Apache-2.0",
-  "version": "1.42.0",
+  "version": "1.52.0",
   "require": {
     "php": ">=7.0.0"
   },