Update for Elixir 1.0.0

Updates for compatability with elixir 1.0.0

Also i reworked the way the OTP application works. It can now be included in a consumers application and automatically started and configured by the consuming applications supervisor. I took the approach from Ecto, but i am very new to elixir so this may be the wrong way to do things.

In my app I use it like this


```
defmodule RiakClient do
  use Riak

  def conf do
    host = System.get_env("RIAK_HOST") || "127.0.0.1"
    port = System.get_env("RIAK_PORT") || "8087"
    host = to_char_list(host)
    port = elem(Integer.parse(port), 0)
    Riak.configure(host: host, port: port)
  end

end
```

And in my supervisor
```
defmodule Struct do
  use Application

  # See http://elixir-lang.org/docs/stable/elixir/Application.html
  # for more information on OTP Applications
  def start(_type, _args) do
    import Supervisor.Spec, warn: false

    children = [worker(Repo, []), worker(RiakClient, [])]

    opts = [strategy: :one_for_one, name: Struct.Supervisor]
    Supervisor.start_link(children, opts)
  end
end
```

let me know about the downfalls of this.