Added installation, usage and example to readme

README.md

@@ -2,3 +2,22 @@ shrthnd.js
 ==========
 
 Makes your CSS files lighter and more readable by converting and combining properties into their shorthand versions when possible.
+
+## Installation
+
+    npm install shrthnd
+
+## Usage
+
+The module takes a CSS string as only parameter and returns an object containing two properties:
+
+* **string**: The shorthanded CSS string
+* **longPropertiesPositions**: An array containing the position (row & column in input string) of the properties that have been shorthanded
+
+## Example
+
+    var cssString = 'body { background-image: url(/img/meow.jpg); background-position: top center; }';
+
+    var shrthnd = require('shrthnd');
+    var shorthandedCss = shrthnd(cssString);
+    console.log(shorthandedCss.string);