Roll back to swift-tools-version 5.1

Author: paulofaria

.swift-version

@@ -1 +1 @@
-5.2
+5.1

.travis.yml

@@ -1,7 +1,7 @@
 language: generic
 env:
   global:
-  - SWIFT_VERSION=5.2
+  - SWIFT_VERSION=5.1
 matrix:
   include:
     - os: osx

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.2
+// swift-tools-version:5.1
 import PackageDescription
 
 let package = Package(

README.md

@@ -21,7 +21,7 @@ This repo only contains the core GraphQL implementation. For a better experience
 
 This project is released under the MIT license. See [LICENSE](LICENSE) for details.
 
-[swift-badge]: https://img.shields.io/badge/Swift-5.2-orange.svg?style=flat
+[swift-badge]: https://img.shields.io/badge/Swift-5.1-orange.svg?style=flat
 [swift-url]: https://swift.org
 [mit-badge]: https://img.shields.io/badge/License-MIT-blue.svg?style=flat
 [mit-url]: https://tldrlegal.com/license/mit-license