Upgrade ESLint to v2.4.0 (#20042)

Refs #19908.

[skip sauce]
[skip validator]

grunt/npm-shrinkwrap.json

@@ -916,9 +916,9 @@
       "resolved": "https://registry.npmjs.org/escope/-/escope-3.6.0.tgz"
     },
     "eslint": {
-      "version": "2.3.0",
-      "from": "eslint@2.3.0",
-      "resolved": "https://registry.npmjs.org/eslint/-/eslint-2.3.0.tgz",
+      "version": "2.4.0",
+      "from": "eslint@2.4.0",
+      "resolved": "https://registry.npmjs.org/eslint/-/eslint-2.4.0.tgz",
       "dependencies": {
         "argparse": {
           "version": "1.0.7",

package.json

@@ -38,7 +38,7 @@
   "devDependencies": {
     "autoprefixer": "^6.0.3",
     "babel-eslint": "^6.0.4",
-    "eslint": "^2.3.0",
+    "eslint": "^2.4.0",
     "grunt": "^0.4.5",
     "grunt-babel": "^5.0.3",
     "grunt-build-control": "^0.6.0",