Allow customizing the text to display poll dates

Since we were using `I18n.t`, our monkey-patch of the `t` helper wasn't
being applied.

app/components/polls/poll_component.rb

@@ -9,6 +9,6 @@ class Polls::PollComponent < ApplicationComponent
   private
 
     def dates
-      I18n.t("polls.dates", open_at: l(poll.starts_at.to_date), closed_at: l(poll.ends_at.to_date))
+      t("polls.dates", open_at: l(poll.starts_at.to_date), closed_at: l(poll.ends_at.to_date))
     end
 end

spec/components/polls/poll_component_spec.rb

@@ -42,6 +42,7 @@ describe Polls::PollComponent do
     end
   end
 
+  describe "dates" do
     it "renders the dates inside an HTML tag" do
       poll = create(:poll, starts_at: "2015-07-15", ends_at: "2015-07-22")
 
@@ -50,6 +51,18 @@ describe Polls::PollComponent do
       expect(page).to have_css ".dates", exact_text: "From 2015-07-15 to 2015-07-22"
     end
 
+    it "allows customizing the text to display dates" do
+      poll = create(:poll, starts_at: "2015-07-15", ends_at: "2015-07-22")
+      create(:i18n_content, key: "polls.dates", value: "Starts someday and finishes who-knows-when")
+
+      render_inline Polls::PollComponent.new(poll)
+
+      expect(page).to have_css ".dates", exact_text: "Starts someday and finishes who-knows-when"
+      expect(page).not_to have_content "2015-07-15"
+      expect(page).not_to have_content "2015-07-22"
+    end
+  end
+
   it "shows a link to poll stats if enabled" do
     poll = create(:poll, :expired, name: "Poll with stats", stats_enabled: true)