Added support iOS 11.

Author: ivanvorobei

Example App/SPAlert.xcodeproj/project.xcworkspace/xcuserdata/ivanvorobei.xcuserdatad/UserInterfaceState.xcuserstate

@@ -9,7 +9,7 @@ Pod::Spec.new do |s|
   s.author = { 'Ivan Vorobei' => '[email protected]' }
 
   s.swift_version = '5.1'
-  s.ios.deployment_target = '12.0'
+  s.ios.deployment_target = '11.0'
 
   s.source_files = 'Sources/SPAlert/**/*.swift'