Reverting podspec to Mixpanel 3.3.9 (davide-scalzo#173)

* Reverting podspec to Mixpanel 3.3.9

* chore: Changed compile to implementation

Author: wkoutre

react-native-mixpanel.podspec

@@ -9,6 +9,6 @@ Pod::Spec.new do |s|
   s.source       = { :git => "https://github.com/davodesign84/react-native-mixpanel.git" }
   s.source_files = 'RNMixpanel/*'
   s.platform     = :ios, "7.0"
-  s.dependency 'Mixpanel', '~> 3.4.5'
+  s.dependency 'Mixpanel', '~> 3.3.9'
   s.dependency 'React'
 end