TODO

Add applicative for shrinking?
Fix bug with genericShrink on Integer
Fix collection of labels in conjunction and disjunction
Allow using unicode characters in Function instance for Char

Add tests for Positive (Small Int) and Small (Positive Int) - or
perhaps a property that combines many modifiers.

Edit new documentation.

To make a release:
* Run build-all script.
* Bump version number in cabal file, in source-repository link, and in test-suite stanza.
* Tag git repo.

Koen's old TODO (trimmed):
* consider adding all QuickCheck1 flags (in particular: printing the number of test cases)
* remove unnecessary incompatibilities with QuickCheck1
* find consistent good names for functions (especially primed function names and callbacks)
* add more callback functions
* implement pre-test callbacks (add these as a top-level flag)
* find a good principle to decide what to export and what not
* decide what to export in Test.QuickCheck
* consider introducing special wrapper modules for certain extensions (such as callbacks)
* Deriving arbitrary, coarbitrary, shrink

More recently:
* Unify CoArbitrary and FunArbitrary?
* Make the testing loop more modular, and provide combinators for
  controlling when to stop testing, how to vary size, etc.
* Some general way of recording information inside a property.
* Add the 'infinite' combinator and use it to experiment with e.g.
  partial generators, sized-based generators.
* Reformat things---some lines are 120 characters long!!!
* Maybe split Property.Result into two parts, environment and result,
  so that we can include Property.Result in Test.Result.
* Perhaps make Gen (Rose a) a first-class thing (maybe for internal
  use only).