default to Swift 4.1

Author: Christian Compton

manifest.yml

@@ -28,7 +28,7 @@ dependencies:
   - name: swift
     version: 4.1
     uri: https://swift.org/builds/swift-4.1-release/ubuntu1404/swift-4.1-RELEASE/swift-4.1-RELEASE-ubuntu14.04.tar.gz
-    md5: d8edd878c9144232aa88ef1ca7f1c242
+    md5: 1c7c620a276102baa23bd7e094fa6096
     cf_stacks:
       - cflinuxfs2
   - name: swift