Add example to README

Author: matthewwithanm

README.md

@@ -1,4 +1,33 @@
 react-google-analytics
 ======================
 
-This inserts an up-to-date Google Analytics object whether Google updates their script or not
+Adds the Google Analytics script to your page and exposes the `ga` tracking
+function as a module.
+
+Usage:
+
+```javascript
+var ga = require('react-google-analytics');
+var GAInitiailizer = ga.Initializer;
+
+// Use the initializer to add the script to your page somewhere.
+var MyComponent = React.createClass({
+  render: function() {
+    return (
+      <div>
+        // SNIP
+          <GAInitiailizer />
+        // SNIP
+      </div>
+    );
+  }
+});
+```
+
+Elsewhere, use the `ga` function:
+
+```javascript
+var ga = require('react-google-analytics');
+ga('create', 'UA-XXXX-Y', 'auto');
+ga('send', 'pageview');
+```