Revive codeclimate badge

Author: osamingo

.codeclimate.yml

@@ -11,3 +11,4 @@ ratings:
     - "*.go"
 exclude_paths:
   - vendor/
+  - "*_test.go"

README.md

@@ -5,6 +5,7 @@
 [![Test Coverage](https://api.codeclimate.com/v1/badges/e820b394cdbd47103165/test_coverage)](https://codeclimate.com/github/osamingo/jsonrpc/test_coverage)
 [![Go Report Card](https://goreportcard.com/badge/osamingo/jsonrpc)](https://goreportcard.com/report/osamingo/jsonrpc)
 [![codebeat badge](https://codebeat.co/badges/cbd0290d-200b-4693-80dc-296d9447c35b)](https://codebeat.co/projects/github-com-osamingo-jsonrpc)
+[![Maintainability](https://api.codeclimate.com/v1/badges/e820b394cdbd47103165/maintainability)](https://codeclimate.com/github/osamingo/jsonrpc/maintainability)
 [![GoDoc](https://godoc.org/github.com/osamingo/jsonrpc?status.svg)](https://godoc.org/github.com/osamingo/jsonrpc)
 [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/osamingo/jsonrpc/master/LICENSE)