podspec fixed

Author: RealBonus

.swift-version

@@ -18,6 +18,7 @@ Pod::Spec.new do |s|
   s.author           = { 'realbonus' => 'p.anokhov@gmail.com' }
   s.source           = { :git => 'https://github.com/realbonus/FreakingSimpleRoundImageView.git', :tag => s.version.to_s }
 
+  s.swift_version = '4.2'
   s.ios.deployment_target = '8.0'
 
   s.source_files = 'FreakingSimpleRoundImageView/Classes/**/*'