TokenStore - Define init/1 required by behaviour GenServer

[nitinstp23]

Getting this warning message on compilation -

warning: function init/1 required by behaviour GenServer is not implemented (in module Goth.TokenStore).

We will inject a default implementation for now:

    def init(args) do
      {:ok, args}
    end

But you want to define your own implementation that converts the arguments given to GenServer.start_link/3 to the server state

[peburrows]

Thanks, I've merged #36 and published to hex as 0.8.1!

[nitinstp23]

@peburrows Cool 👍