Set Swift version by using new attribute swift_versions

Author: dangthaison91

.swift-version

@@ -10,7 +10,7 @@ Pod::Spec.new do |s|
 
      s.ios.deployment_target = '9.0'
      s.requires_arc = true
-     s.swift_version = '5.0'
+     s.swift_versions = '5.0'
 
      s.source_files  = "Sources/**/*.swift"
      s.framework  = "Foundation"