Create an example of using the reader monad
Rename "state" to "config"
Derive functor and applicative instances too
Add a motivating comment

Mostly copied from `globalstate.hs`.
Use aeson's eitherDecode instead of just decode
Merge pull request #125 from k-bx/either-decode

Use aeson's eitherDecode instead of just decode
Add more tests
Depend on hspec-2.*
Merge pull request #129 from scotty-web/update-hspec

Depend on hspec-2.*