chore(README) update

Author: davidchase

README.md

@@ -1,2 +1,17 @@
 # path-union
 > Create a union between two paths
+
+
+## Usage
+Given two paths find the union between them.
+
+
+
+```js
+const union = require('path-union')
+
+const src = '/Users/davidchase/Desktop/github/path-union/fixtures/packages'
+const dest = '/Users/davidchase/Desktop/github/path-union/dist'
+
+union(dest, src) // => /Users/davidchase/Desktop/github/path-union/dist/fixtures/packages
+```