Enable the for-direction ESLint rule

See https://eslint.org/docs/rules/for-direction; helps avoid typos that would cause infinite `for` loops.

Also, updates `eslint` and `eslint-plugin-mozilla` to the latest available versions.

.eslintrc

@@ -19,6 +19,7 @@
 
   "rules": {
     // Possible errors
+    "for-direction": "error",
     "no-cond-assign": ["error", "except-parens"],
     "no-constant-condition": ["error", { "checkLoops": false, }],
     "no-dupe-args": "error",

package.json

@@ -9,8 +9,8 @@
     "babel-preset-es2015": "^6.24.1",
     "core-js": "^2.5.0",
     "escodegen": "^1.8.0",
-    "eslint": "^4.2.0",
-    "eslint-plugin-mozilla": "^0.4.0",
+    "eslint": "^4.5.0",
+    "eslint-plugin-mozilla": "^0.4.3",
     "gulp": "^3.9.1",
     "gulp-rename": "^1.2.2",
     "gulp-replace": "^0.5.4",