Update podspec

Author: pvzig

SlackKit.podspec

@@ -10,7 +10,7 @@ Pod::Spec.new do |s|
   s.ios.deployment_target = '8.0'
   s.osx.deployment_target = '10.9'
   s.requires_arc = true
-  s.source_files = 'SlackKit/**/*'  
+  s.source_files = 'SlackKit/*.swift'  
   s.frameworks = 'Foundation'
   s.dependency 'Starscream', '~> 1.0.1'
 end