Support multiple tracking calls

If you redirect and use event persisting, only the first event would
get tracked. By setting rack.session correctly mixpanel will add extra
events to the already existing queue.

Author: bittersweet

example/app/controllers/posts_controller.rb

@@ -69,4 +69,11 @@ def destroy
       format.json { head :no_content }
     end
   end
+
+  # Useful for testing if every event gets tracked when using persist: true.
+  def redirect
+    @post = Post.find(params[:id])
+    track_action '[redirect] post', post_id: @post.id
+    redirect_to @post
+  end
 end

example/config/routes.rb

@@ -1,5 +1,7 @@
 Example::Application.routes.draw do
-  resources :posts
+  resources :posts do
+    get :redirect, on: :member
+  end
 
   # The priority is based upon order of creation:
   # first created -> highest priority.

lib/ab_panel/controller_additions.rb

@@ -55,7 +55,7 @@ def initialize_ab_panel!(options = {})
 
       {
         'distinct_id' => distinct_id,
-        'rack.session' => request['rack.session'],
+        'rack.session' => request.env['rack.session'],
         'ip' => request.remote_ip
       }.each do |key, value|
         AbPanel.set_env(key, value)
@@ -113,8 +113,6 @@ def track_action(name, properties = {})
 
       AbPanel.identify(distinct_id)
       AbPanel.track(name, options.merge(ab_panel_options))
-
-      session['mixpanel_events'] ||= AbPanel.env['rack.session']['mixpanel_events'] rescue []
     end
   end
 end