chore(deps): update eslint to version 5.4.0

Also:
- update the packages related to it to their latest versions.
- remove 'eslint-plugin-react' (unused).
- add 'eslint-plugin-import' and 'eslint-plugin-node' (required by standard).
- fix new whitespace violation found by eslint.

Closes #235.

package.json

@@ -26,18 +26,19 @@
     "lodash": "^4.17.10"
   },
   "devDependencies": {
-    "eslint": "^2.13.1",
-    "eslint-config-standard": "^5.3.1",
-    "eslint-plugin-promise": "^1.3.2",
-    "eslint-plugin-react": "^5.2.2",
-    "eslint-plugin-standard": "^1.3.2",
+    "eslint": "^5.4.0",
+    "eslint-config-standard": "^11.0.0",
+    "eslint-plugin-import": "^2.14.0",
+    "eslint-plugin-node": "^7.0.1",
+    "eslint-plugin-promise": "^4.0.0",
+    "eslint-plugin-standard": "^3.1.0",
     "expect.js": "^0.3.1",
     "grunt": "^1.0.1",
     "grunt-bump": "0.8.0",
     "grunt-contrib-watch": "^1.0.0",
     "grunt-conventional-changelog": "^6.1.0",
     "grunt-conventional-github-releaser": "^1.0.0",
-    "grunt-eslint": "^18.1.0",
+    "grunt-eslint": "^21.0.0",
     "grunt-npm": "0.0.2",
     "karma": "^1.0.0",
     "karma-chrome-launcher": "^1.0.0",

tasks/grunt-karma.js

@@ -113,7 +113,7 @@ module.exports = function (grunt) {
     // allow karma to be run in the background so it doesn't block grunt
     if (data.background) {
       var backgroundProcess = require('child_process').fork(
-          path.join(__dirname, '..', 'lib', 'background.js')
+        path.join(__dirname, '..', 'lib', 'background.js')
       )
 
       backgroundProcess.on('close', function (code) {