Have the vote_range function accept a max_range argument

This argument is the maximal value the user can give to its vote.
If none is provided, it defaults to the number of candidates which is the
default range voting mechanism
Update the information message according to the type of voting used for this election
Offer the simplified range voting (max range = 3) in the options when creating an election
If the election is of type range_3, call the appropriately vote_range
Merge pull request #28 from fedora-infra/simplified_range

Simplified range