Contravariant Coyoneda, with tests for Order.
Make ContravariantCoyoneda more like Coyoneda.
Flip members.
Remove self binding; it is unused.
Scaladoc for the abstract members of *Coyoneda.
Move the schwartzian* members to tests.
Replace Coyoneda.apply with a fully-powered version.

* The old Coyoneda.apply is now called 'lift'.

* Both *Coyoneda have 'unlift' aliases for 'run'.

* More construction facilities for Coyoneda copied from
  ContravariantCoyoneda.

* Coyoneda is now sealed.

* Coyoneda only has abstract values now, no abstract methods, and
  there is only one (private) concrete class.
Flip the apply arguments and remove most implicits.
Minor doc fixes.
Start a ContravariantCoyoneda example.
ContravariantCoyoneda example: most of the basics.
Finish contravariant coyoneda example.
2.9.3 compilation.
Another property needed to derive associativity.
Transpose args, refer to usage example in ContravariantCoyoneda doc.
The InvariantFunctor rule isn't strong enough; just require associativity directly.
Fix indentation after <-.
Dangling comment.
Merge pull request #677 from S11001001/topic/coyoneda-contravariant-coyoneda

Contravariant coyoneda; move Coyoneda API around a bit