Merge pull request #125 from mixpanel/bump-ios-3.1.2

bump iOS SDK to v3.1.2

Author: zihejia

MixpanelReactNative.podspec

@@ -19,5 +19,5 @@ Pod::Spec.new do |s|
   s.pod_target_xcconfig = { 'DEFINES_MODULE' => 'YES' }  
 
   s.dependency "React"
-  s.dependency "Mixpanel-swift", '3.1.0'
+  s.dependency "Mixpanel-swift", '3.1.2'
 end