Add Documentation using YARD.
Work around step definition bug in `yard_cucumber`

Classes linked with {Class} cause `yard_cucumber` to fail to display the
step definition documentation. Use `Class` instead.
First pass at porting multi-dance scoring.
Create `SubPlacement` model

It stores the placements for `SubEvent` models. The scoring of
single-dance events will need to be changed to create the appropriate
`SubPlacement` models.
Fix typo copied over from website

The World Salsa Federation site I am using as a reference had couple 55
listed twice. Slightly disconcerting that this wasn't caught before...
Begin testing multi-dance scoring
Use Cucumber's `Table#diff!` to simplify steps

It also provides better failure info than a loop of `Array#includes?`
calls.
Order {Sub,}Placement association by rank