Adding Airbnb ESLint rules

Disable usupported rules for specific ember apps.
Add a eslint-config-airbnb-base, eslint-plugin-ember,
eslint-plugin-import to package.json.
Update ember-cli-code-coverage to v1.0.0-beta.4 version
to get the fix when using the `useBabelInstrumenter` config
see ember-cli-code-coverage/ember-cli-code-coverage#133 .

Closes #58

Author: bekicot

.eslintrc.js

@@ -10,12 +10,24 @@ module.exports = {
   ],
   extends: [
     'eslint:recommended',
-    'plugin:ember/recommended'
+    'plugin:ember/recommended',
+    'airbnb-base'
   ],
   env: {
     browser: true
   },
   rules: {
+    // This rule has no support for @ember import system.
+    // Ember build have their own mechanism to managing dependency.
+    // Ember build will raise error on build if there is an import error.
+    'import/extensions': 'off',
+    'import/no-unresolved': 'off',
+    'import/no-extraneous-dependencies': 'off',
+    // Ember use underscore dangling, e.g _super. Which is enforced by ember's
+    // own linter to be used on init() method.
+    'no-underscore-dangle': 'off',
+    // Ember Routes and tests utilize `this` inside their callback.
+    'prefer-arrow-callback': 'off',
   },
   overrides: [
     // node files

config/coverage.js

@@ -0,0 +1,7 @@
+/* global module */
+
+'use strict';
+
+module.exports = {
+  useBabelInstrumenter: true,
+};

package.json

@@ -26,7 +26,7 @@
     "ember-cli": "~3.1.4",
     "ember-cli-app-version": "^3.2.0",
     "ember-cli-babel": "^6.6.0",
-    "ember-cli-code-coverage": "^0.4.2",
+    "ember-cli-code-coverage": "^1.0.0-beta.4",
     "ember-cli-dependency-checker": "^2.0.0",
     "ember-cli-eslint": "^4.2.1",
     "ember-cli-htmlbars": "^2.0.1",
@@ -43,7 +43,9 @@
     "ember-paper": "^1.0.0-alpha.19",
     "ember-source": "~3.1.0",
     "eslint": "^4.19.1",
+    "eslint-config-airbnb-base": "12.1.0",
     "eslint-plugin-ember": "^5.0.0",
+    "eslint-plugin-import": "^2.7.0",
     "github-api": "https://github.com/github-tools/github/archive/v3.1.0.tar.gz",
     "loader.js": "^4.2.3",
     "remark": "^9.0.0",