delete 'Swift 5' branch in README.md - master is on Swift 5

Author: denisenepraunig

README.md

@@ -11,8 +11,7 @@
 
 | Branch | Build Status | Versions |
 |:---------|:--------------:|:----------:|
-| **master** |[![Build Status](https://travis-ci.org/devicekit/DeviceKit.svg?branch=master)](https://travis-ci.org/devicekit/DeviceKit)| - |
-| **Swift 5** |[![Build Status](https://travis-ci.org/devicekit/DeviceKit.svg?branch=swift-5)](https://travis-ci.org/devicekit/DeviceKit)| ≥ 2.0 |
+| **master** |[![Build Status](https://travis-ci.org/devicekit/DeviceKit.svg?branch=master)](https://travis-ci.org/devicekit/DeviceKit)| ≥ 2.0 |
 | **Swift 4 - 4.2** |[![Build Status](https://travis-ci.org/devicekit/DeviceKit.svg?branch=swift-4)](https://travis-ci.org/devicekit/DeviceKit)| ≥ 1.3 < 1.13 |
 | **Swift 3** |[![Build Status](https://travis-ci.org/devicekit/DeviceKit.svg?branch=swift-3)](https://travis-ci.org/devicekit/DeviceKit)| ≥ 1.0 < 1.3 |
 | **Swift 2.3** |[![Build Status](https://travis-ci.org/devicekit/DeviceKit.svg?branch=swift-2.3-unsupported)](https://travis-ci.org/devicekit/DeviceKit)| < 1.0 |