Order translations using ruby

Joining the translations table caused duplicate records to appear.
Ordering with SQL is simply too hard because we need to consider
fallback locales.

Thanks Senén for providing most of the tests in the poll spec.

spec/models/user_spec.rb

@@ -3,7 +3,7 @@ require "rails_helper"
 describe User do
 
   describe "#headings_voted_within_group" do
-    it "returns the headings voted by a user ordered by name" do
+    it "returns the headings voted by a user" do
       user1 = create(:user)
       user2 = create(:user)
 
@@ -35,6 +35,15 @@ describe User do
       expect(user2.headings_voted_within_group(group)).not_to include(san_franciso)
       expect(user2.headings_voted_within_group(group)).not_to include(another_heading)
     end
+
+    it "returns headings with multiple translations only once" do
+      user = create(:user)
+      group = create(:budget_group)
+      heading = create(:budget_heading, group: group, name_en: "English", name_es: "Spanish")
+      create(:vote, votable: create(:budget_investment, heading: heading), voter: user)
+
+      expect(user.headings_voted_within_group(group).count).to eq 1
+    end
   end
 
   describe "#debate_votes" do