Merge pull request #57 from jdnavarro/master

Fix docs
Un-export NumThreads from Test.Tasty and clarify why
Haddocks
Don't use generic-maybe but add a note encouraging its use
Rename CoreOptions to Options.Core
Move suiteOptions from CmdLine to Ingredients
Add singleOption
Derive Monad for Ap
Environment options
Change handling of default options in CLParser