Master and Swift branch throw errors in Swift 4.2


<img width="257" alt="screenshot 2019-02-26 at 21 00 37" src="https://user-images.githubusercontent.com/7126904/53442499-b78b7f00-3a09-11e9-9e53-a435b4d48a1a.png">

Issue environment:

- Xcode Version: 10.1
- iOS Version: 12.1


Issue Details:
Pod throws errors when included in a swift 4.2 project

