def load(name, options = {})
      env_var = options.fetch(:env_var, name.to_s.upcase)
      type = options.fetch(:type, :string)
      required = options.fetch(:required, true)
      @registry[name] = case type
                        when :string then load_string(env_var, required)
                        when :int    then load_int(env_var, required)
                        when :bool   then load_bool(env_var, required)
                        else raise ArgumentError, "Invalid type #{type}"
                        end
    end
def load(name, options = {})
      env_var = options.fetch(:env_var, name.to_s.upcase)
      type = options.fetch(:type, :string)
      required = options.fetch(:required, true)
      @registry[name] = case type
                        when :string then load_string(env_var, required)
                        when :int    then load_int(env_var, required)
                        when :bool   then load_bool(env_var, required)
                        else raise ArgumentError, "Invalid type #{type}"
                        end
    end
Initialise a Registry.

 env - A Hash used as a source for environment variables. Usually, ENV
       will be used.
 See Prius.load for documentation.