Add a "Reviewed by Hound" badge

Author: salbertson

README.md

@@ -4,6 +4,7 @@
 [![CocoaPods](https://img.shields.io/cocoapods/v/Nimble.svg)](https://cocoapods.org/pods/Nimble)
 [![Carthage Compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
 [![Platforms](https://img.shields.io/cocoapods/p/Nimble.svg)](https://cocoapods.org/pods/Nimble)
+[![Reviewed by Hound](https://img.shields.io/badge/Reviewed_by-Hound-8E64B0.svg)](https://houndci.com)
 
 Use Nimble to express the expected outcomes of Swift
 or Objective-C expressions. Inspired by