- migrated DateToolsSwift test project to Swift 5

- cleaned up project warnings by updating visibility modifiers
- updated podspec
- updated swift-version file

Author: MatthewYork

.swift-version

@@ -1 +1 @@
-3.0
+5.0

DateToolsSwift.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name         = 'DateToolsSwift'
-  s.version      = '4.0.0'
+  s.version      = '5.0.0'
   s.summary      = 'Dates and time made easy in Swift'
   s.homepage     = 'https://github.com/MatthewYork/DateTools'