Add prettier setup.

Author: Robert Jackson

.eslintignore

@@ -1,2 +1,3 @@
+!.*
 test/fixtures
-test/helpers
+test/helpers

.eslintrc.js

@@ -1,22 +1,15 @@
 module.exports = {
-    'env': {
-        'browser': true,
-        'node': true,
-        'es6': true,
-    },
-    'extends': ['eslint:recommended', 'plugin:node/recommended'],
-    'parserOptions': {
-        'ecmaVersion': 2017
-    },
-    'rules': {
-        'no-console': ['error', { 'allow': ['warn', 'error']}],
-        'linebreak-style': [
-            'error',
-            'unix'
-        ],
-        'semi': [
-            'error',
-            'always'
-        ]
-    }
+  parserOptions: {
+    ecmaVersion: 2017,
+  },
+  extends: ['eslint:recommended', 'plugin:node/recommended', 'plugin:prettier/recommended'],
+  plugins: ['prettier', 'node'],
+  env: {
+    browser: true,
+    node: true,
+    es6: true,
+  },
+  rules: {
+    'no-console': ['error', { allow: ['warn', 'error'] }],
+  },
 };

.gitignore

@@ -1,3 +1,4 @@
+.eslintcache
 /node_modules
 npm-debug.log
 tmp*

.prettierrc

@@ -0,0 +1,5 @@
+{
+  "singleQuote": true,
+  "printWidth": 100,
+  "trailingComma": "es5"
+}

package.json

@@ -5,7 +5,7 @@
   "main": "src/index.js",
   "scripts": {
     "changelog": "lerna-changelog",
-    "lint:js": "node_modules/.bin/eslint src test",
+    "lint:js": "eslint --cache .",
     "test": "npm run-script lint:js && mocha",
     "preversion": "npm test",
     "postversion": "git push origin master --tags"
@@ -41,13 +41,16 @@
     "chai": "^4.1.0",
     "chai-as-promised": "^7.1.1",
     "ember-source": "3.8.0",
-    "eslint": "^5.10.0",
+    "eslint": "^6.5.1",
+    "eslint-config-prettier": "^6.4.0",
     "eslint-plugin-chai-expect": "^2.0.1",
-    "eslint-plugin-mocha": "^5.2.0",
-    "eslint-plugin-node": "^8.0.0",
+    "eslint-plugin-mocha": "^6.2.0",
+    "eslint-plugin-node": "^10.0.0",
+    "eslint-plugin-prettier": "^3.1.1",
     "express": "^4.15.4",
     "lerna-changelog": "^0.8.2",
     "mocha": "^5.2.0",
+    "prettier": "^1.18.2",
     "rimraf": "^2.6.2",
     "temp": "^0.8.3"
   }