(chore) README: add usage.

README.md

@@ -2,4 +2,78 @@
 
 Userscript metadata parser.
 
-**Work In Progress**
+## Usage
+
+```javascript
+var userscriptText = '...'
+var userscriptParser = require('userscript-parser')
+
+var meta = userscriptParser(userscriptText)
+```
+
+Given this userscript:
+```javascript
+// ==UserScript==
+// @name        Awesome Script
+// @description This script even does the laundry!
+// @downloadURL https://www.example.com/myscript.user.js
+// @homepageURL https://github.com/gantt/downloadyoutube
+// @author      Gantt
+// @version     1.8.3
+// @date        2015-05-17
+// @include     http://www.youtube.com/*
+// @include     https://www.youtube.com/*
+// @exclude     http://www.youtube.com/embed/*
+// @exclude     https://www.youtube.com/embed/*
+// @match       http://www.youtube.com/*
+// @match       https://www.youtube.com/*
+// @match       http://s.ytimg.com/yts/jsbin/html5player*
+// @match       https://s.ytimg.com/yts/jsbin/html5player*
+// @match       http://manifest.googlevideo.com/*
+// @match       https://manifest.googlevideo.com/*
+// @match       http://*.googlevideo.com/videoplayback*
+// @match       https://*.googlevideo.com/videoplayback*
+// @match       http://*.youtube.com/videoplayback*
+// @match       https://*.youtube.com/videoplayback*
+// @grant       GM_xmlhttpRequest
+// @grant       GM_getValue
+// @grant       GM_setValue
+// @run-at      document-end
+// @license     MIT License
+// ==/UserScript==
+
+var mynameis = 'USERSCRIPT!'
+
+```
+
+will produce this meta object:
+
+```javascript
+{
+  name: [ 'Awesome Script' ],
+  description: [ 'This script even does the laundry!' ],
+  downloadURL: [ 'https://www.example.com/myscript.user.js' ],
+  homepageURL: [ 'https://github.com/gantt/downloadyoutube' ],
+  author: [ 'Gantt' ],
+  version: [ '1.8.3' ],
+  date: [ '2015-05-17' ],
+  include: [ 'http://www.youtube.com/*', 'https://www.youtube.com/*' ],
+  exclude:
+   [ 'http://www.youtube.com/embed/*',
+     'https://www.youtube.com/embed/*' ],
+  match:
+   [ 'http://www.youtube.com/*',
+     'https://www.youtube.com/*',
+     'http://s.ytimg.com/yts/jsbin/html5player*',
+     'https://s.ytimg.com/yts/jsbin/html5player*',
+     'http://manifest.googlevideo.com/*',
+     'https://manifest.googlevideo.com/*',
+     'http://*.googlevideo.com/videoplayback*',
+     'https://*.googlevideo.com/videoplayback*',
+     'http://*.youtube.com/videoplayback*',
+     'https://*.youtube.com/videoplayback*' ],
+  grant: [ 'GM_xmlhttpRequest', 'GM_getValue', 'GM_setValue' ],
+  license: [ 'MIT License' ],
+  content: '\n\nvar mynameis = \'USERSCRIPT!\'\n'
+}
+```