Unroll Monad Transformer Stacks Chapter

[doyougnu]

• This causes slowdown due to indirection
• be sure to reference known/unknown function calls
• Show the Stg/Core
• Give guidance on what to do
• Define exactly what unroll means (it means flattening the nested tuple that is the denotation of monad transformers)
• Possible case study?

[doyougnu]

From the proposal:

2.2.14 Removing monad transformer stacks: 
 - ReaderT, replace with `reflection` or `ImplicitParams`. 
 - Remove StateT for STRefs IORefs
 - Remove ExceptT, then throw/catch in IO instead