Drop Rails3 support

app/models/category.rb

@@ -5,17 +5,10 @@ class Category < ActiveRecord::Base
   include Concern::Positionable
 
   belongs_to :topic, dependent: :destroy
-  if rails4?
-    belongs_to :topic_only_relative_url,
-                -> { select "id, title, slug" },
-                class_name: "Topic",
-                foreign_key: "topic_id"
-  else
-    belongs_to :topic_only_relative_url,
-                select: "id, title, slug",
-                class_name: "Topic",
-                foreign_key: "topic_id"
-  end
+  belongs_to :topic_only_relative_url,
+              -> { select "id, title, slug" },
+              class_name: "Topic",
+              foreign_key: "topic_id"
 
   belongs_to :user
   belongs_to :latest_post, class_name: "Post"
@@ -81,7 +74,7 @@ class Category < ActiveRecord::Base
 
   def self.scoped_to_permissions(guardian, permission_types)
     if guardian && guardian.is_staff?
-      rails4? ? all : scoped
+      all
     else
       permission_types = permission_types.map{ |permission_type|
         CategoryGroup.permission_types[permission_type]

app/models/discourse_version_check.rb

@@ -1,17 +1,5 @@
 class DiscourseVersionCheck
-  if rails4?
-    include ActiveModel::Model
-  else
-    include ActiveAttr::Attributes
-    include ActiveAttr::MassAssignment
-    include ActiveModel::Serialization
-  end
+  include ActiveModel::Model
 
   attr_accessor :latest_version, :critical_updates, :installed_version, :installed_sha, :missing_versions_count, :updated_at, :version_check_pending
-
-  unless rails4?
-    def active_model_serializer
-      DiscourseVersionCheckSerializer
-    end
-  end
 end

app/models/incoming_links_report.rb

@@ -90,7 +90,6 @@ class IncomingLinksReport
     num_clicks = num_clicks.to_a.sort_by {|x| x[1]}.last(10).reverse # take the top 10
     report.data = []
     topics = Topic.select('id, slug, title').where('id in (?)', num_clicks.map {|z| z[0]})
-    topics = topics.all unless rails4?
     num_clicks.each do |topic_id, num_clicks_element|
       topic = topics.find {|t| t.id == topic_id}
       if topic

app/models/invite.rb

@@ -103,7 +103,7 @@ class Invite < ActiveRecord::Base
         filter: "%#{email_or_username.downcase}%"
       )
     else
-      rails4? ? all : scoped
+      all
     end
   end
 

app/models/topic.rb

@@ -69,10 +69,6 @@ class Topic < ActiveRecord::Base
     self.title = TextCleaner.clean_title(TextSentinel.title_sentinel(title).text) if errors[:title].empty?
   end
 
-  unless rails4?
-    serialize :meta_data, ActiveRecord::Coders::Hstore
-  end
-
   belongs_to :category
   has_many :posts
   has_many :topic_allowed_users

app/models/topic_featured_users.rb

@@ -11,7 +11,6 @@ class TopicFeaturedUsers
 
   # Chooses which topic users to feature
   def choose(args={})
-    topic.reload unless rails4?
     clear
     update keys(args)
     update_participant_count

app/models/user_email_observer.rb

@@ -60,11 +60,7 @@ class UserEmailObserver < ActiveRecord::Observer
   end
 
   def after_commit(notification)
-    transaction_includes_action = if rails4?
-      notification.send(:transaction_include_any_action?, [:create])
-    else
-      notification.send(:transaction_include_action?, :create)
-    end
+    transaction_includes_action = notification.send(:transaction_include_any_action?, [:create])
 
     delegate_to_email_user notification if transaction_includes_action
   end