Docs: update README.md

Author: mysticatea

README.md

@@ -22,11 +22,13 @@ $ npm-run-all --parallel watch:*
 
 ## Installation
 
-```
-$ npm install npm-run-all
+```bash
+$ npm install npm-run-all --save-dev
+# or
+$ yarn add npm-run-all --dev
 ```
 
-- It requires `Node@>=4` and `npm@>=2`
+- It requires `Node@>=4`.
 - The `npm-run-all` package introduces 3 CLI commands: `npm-run-all`, `run-s`, and `run-p`.
 
 ## CLI Commands

package.json

@@ -13,8 +13,7 @@
     "lib"
   ],
   "engines": {
-    "node": ">= 4",
-    "npm": ">= 2"
+    "node": ">= 4"
   },
   "scripts": {
     "_mocha": "mocha \"test/*.js\" --compilers js:babel-register --timeout 60000",