default to Swift 4.1

Author: Christian Compton

manifest.yml

@@ -34,7 +34,7 @@ dependencies:
   - name: swift
     version: 4.0.3
     uri: https://swift.org/builds/swift-4.0.3-release/ubuntu1404/swift-4.0.3-RELEASE/swift-4.0.3-RELEASE-ubuntu14.04.tar.gz
-    md5: c23cfe01fcfd363c1acb20f6cbe2c30b
+    md5: d8edd878c9144232aa88ef1ca7f1c242
     cf_stacks:
       - cflinuxfs2
   - name: clang