Store remote votes URI (#10158)

* Store remote votes URI

* Add spec for accepting remote votes

* Make poll vote id generation work the same way as follows

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2019_02_26_003449) do
+ActiveRecord::Schema.define(version: 2019_03_04_152020) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -447,6 +447,7 @@ ActiveRecord::Schema.define(version: 2019_02_26_003449) do
     t.integer "choice", default: 0, null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.string "uri"
     t.index ["account_id"], name: "index_poll_votes_on_account_id"
     t.index ["poll_id"], name: "index_poll_votes_on_poll_id"
   end