Fix service coverage script and linting (#975)

* Fix "callback is not a function" in coverage:test:services

* Don't lint /coverage

.eslintignore

@@ -0,0 +1 @@
+/coverage

package.json

@@ -37,7 +37,7 @@
   },
   "scripts": {
     "coverage:test:js": "istanbul cover _mocha '*.spec.js' 'lib/*.spec.js' --dir coverage/js",
-    "coverage:test:services": "istanbul cover _mocha --delay service-tests/runner/cli.js --dir coverage/services",
+    "coverage:test:services": "istanbul cover _mocha service-tests/runner/cli.js --dir coverage/services -- --delay",
     "coverage:test": "npm run coverage:test:js && npm run coverage:test:services",
     "coverage:report": "istanbul report",
     "coverage:report:reopen": "opn coverage/lcov-report/index.html",

service-tests/README.md

@@ -259,12 +259,10 @@ By checking code coverage, we can make sure we've covered all our bases.
 We can generate a coverage report and open it:
 
 ```
-npm run coverage:test:services -- -- --only=travis
+npm run coverage:test:services -- --only=travis
 npm run coverage:report:open
 ```
 
-Note the two sets of double dashes.
-
 After searching `server.js` for the Travis code, we see that we've missed a
 big block: the error branch in the request callback. To test that, we simulate
 network connection errors on any unmocked requests.