Decouple tests from unspecified data ordering

These tests have been passing with SQLite, but don't reflect guaranteed
behavior and with PostgreSQL failed intermittently.

spec/controllers/api/v1/events_controller_spec.rb

@@ -15,9 +15,7 @@ describe Api::V1::EventsController do
         json = JSON.parse(response.body)['events']
         expect(response).to be_success
 
-        expect(json.length).to eq(2)
-        expect(json[0]['title']).to eq('Example Event')
-        expect(json[1]['title']).to eq('Conference Event')
+        expect(json.map { |e| e['title'] }).to contain_exactly('Conference Event', 'Example Event')
       end
     end