electsys21 0.1.0

• Initial release.
• Voting methods for ranked, rated and approval ballots: the D21 (with and without minus votes), first-past-the-post, two-round runoff, instant runoff, the Borda count, approval voting, majority judgement and the Condorcet method.
• Automatic detection of ballot input type (ranking, cardinal utilities, approvals and scores), configurable tie-breaking and tidy summaries of the results.
• Ballot generators for simulation: gen_ranks(), gen_utilities() and gen_approvals().