Relieve ios deployment version to 7.0
diff --git a/gRPC-Core.podspec b/gRPC-Core.podspec
index 8b67a5d..9cb5552 100644
--- a/gRPC-Core.podspec
+++ b/gRPC-Core.podspec
@@ -51,7 +51,7 @@
     :submodules => true,
   }
 
-  s.ios.deployment_target = '7.1'
+  s.ios.deployment_target = '7.0'
   s.osx.deployment_target = '10.9'
   s.requires_arc = false