Split up [github] testers (#2560)

- Update github contributors badge for `create-service-tester`.

services/github/github-search.tester.js

@@ -0,0 +1,16 @@
+'use strict'
+
+const Joi = require('joi')
+const { isMetric } = require('../test-validators')
+
+const t = (module.exports = require('../create-service-tester')())
+
+t.create('hit counter')
+  .get('/torvalds/linux/goto.json')
+  .timeout(10000)
+  .expectJSONTypes(Joi.object().keys({ name: 'goto counter', value: isMetric }))
+
+t.create('hit counter for nonexistent repo')
+  .get('/torvalds/not-linux/goto.json')
+  .timeout(10000)
+  .expectJSON({ name: 'goto counter', value: 'repo not found' })