Fix typo.

README.md

 
 * [Pomander](https://github.com/tamagokun/pomander) - A deployment tool for PHP applications.
 * [Rocketeer](https://github.com/Anahkiasen/rocketeer) - A fast and easy deployer for the PHP world.
-* [Envoy](https://github.com/laravel/envoy) - An tool to run SSH tasks with PHP.
+* [Envoy](https://github.com/laravel/envoy) - A tool to run SSH tasks with PHP.
 
 ## Third Party APIs
 *Libraries for accessing third party APIs.*