drop node 6 support

.travis.yml

@@ -1,8 +1,7 @@
 sudo: false
 language: node_js
 node_js:
-  - "10"
-  - "8"
-  - "6"
+  - '10'
+  - '8'
 after_success:
   - npm run coveralls

appveyor.yml

@@ -1,14 +1,13 @@
 # https://www.appveyor.com/docs/appveyor-yml
 
-version: "{build}"
+version: '{build}'
 
 clone_depth: 10
 
 environment:
   matrix:
-    - nodejs_version: "10"
-    - nodejs_version: "8"
-    - nodejs_version: "6"
+    - nodejs_version: '10'
+    - nodejs_version: '8'
 
 install:
   - ps: Install-Product node $env:nodejs_version

package.json

@@ -4,8 +4,8 @@
   "description": "Inline critical-path css and load the existing stylesheets asynchronously",
   "main": "index.js",
   "scripts": {
-    "test": "xo && nyc mocha test/index.js --timeout 5000",
-    "coveralls": "nyc report --reporter=text-lcov | coveralls"
+    "test": "xo && jest --coverage",
+    "coveralls": "cat ./coverage/lcov.info | coveralls"
   },
   "files": [
     "index.js",
@@ -35,6 +35,7 @@
     "detect-indent": "5.0.0",
     "dom-serializer": "0.1.0",
     "fg-loadcss": "^2.0.1",
+    "fs-extra": "^7.0.1",
     "get-stdin": "^6.0.0",
     "indent-string": "^3.2.0",
     "lodash": "^4.17.11",
@@ -49,23 +50,31 @@
     "chai": "^4.0.2",
     "concat-stream": "^1.6.2",
     "coveralls": "^3.0.2",
+    "execa": "^1.0.0",
+    "jest": "^23.6.0",
     "mocha": "^5.2.0",
     "mockery": "^2.1.0",
     "nyc": "^13.0.1",
     "read-package-json": "^2.0.10",
+    "read-pkg-up": "^4.0.0",
     "xo": "^0.23.0"
   },
   "xo": {
-    "space": 4,
-    "envs": [
-      "node",
-      "mocha"
-    ],
-    "ignores": [
-      "test/*.js"
+    "space": 2,
+    "prettier": true
+  },
+  "jest": {
+    "roots": [
+      ""
     ]
   },
+  "prettier": {
+    "trailingComma": "es5",
+    "singleQuote": true,
+    "printWidth": 120,
+    "bracketSpacing": false
+  },
   "engines": {
-    "node": ">= 6"
+    "node": ">= 8"
   }
 }