People's choice map voting

[twelch]

• Allow up to one vote per person per map.
• Voting is done from the detail view for an individual map, click a button to vote
• Once they click to vote, they should be able to click to unvote
• Votes should be stored in a simple Ninja form, tying the user to the unique map id.
• Will need some checks on page load to see if the user has already voted in order to set the state of the vote button properly and to prevent double voting.

[twelch]

Totally done, except the unvote