Modify Main page to go to result page if user already voted

[RebeccaSyria]

If a user has already voted, they should be able to click a button for "view results" instead of "join vote".
This will probably involve modifying the pollList sent from the backend to include a "userVoted" boolean for each poll for that user, then we can use that to display either "view results" or "join vote"
View results page itself is issue #16, so this should be done after that, or use a dummy page