Update podspec to include multiple Swift versions

Author: keith

Kronos.podspec

@@ -1,12 +1,12 @@
 Pod::Spec.new do |s|
   s.name = 'Kronos'
-  s.version = '4.1.0'
+  s.version = '4.1.1'
   s.license = { :type => 'Apache License, Version 2.0', :file => 'LICENSE' }
   s.summary = 'Elegant NTP client in Swift'
   s.homepage = 'https://github.com/lyft/Kronos'
   s.authors = { 'Martin Conte Mac Donell' => '[email protected]' }
   s.source = { :git => 'https://github.com/Lyft/Kronos.git', :tag => s.version }
-  s.swift_version = '5'
+  s.swift_versions = ['5.0', '5.2']
 
   s.ios.deployment_target = '8.0'
   s.osx.deployment_target = '10.9'