A monoid, functor, applicative, monad, and arrow library

This is currently very Haskell-flavoured. It will become more idiomatic after the first pass.

If available in Hex, the package can be installed as:

1. Add witchcraft to your list of dependencies in mix.exs:

   def deps do [{:witchcraft, "~> 0.0.1"}] end

2. Ensure witchcraft is started before your application:

   def application do [applications: [:witchcraft]] end