Added infrastructure to support simple natural transformations; more examples.
Added infrastructure to support simple natural transformations; more examples.

liff/shapeless,lambdista/shapeless,roberth/shapeless,isaka/shapeless,lukasz-golebiewski/shapeless,Atry/shapeless,tek/shapeless,notxcain/shapeless,retronym/shapeless,TomasMikula/shapeless,wheaties/shapeless,khronnuz/shapeless,milessabin/shapeless,joescii/shapeless,malcolmgreaves/shapeless,clhodapp/shapeless,fthomas/shapeless,alexarchambault/shapeless,triggerNZ/shapeless