Put required response_type parameter

[brauliobo]

The required response_type parameter is missing (ref. http://tools.ietf.org/html/rfc6749#section-3.1.1)

[coveralls]

Coverage decreased (-19.1%) when pulling d5039b0 on coletivoEITA:master into 6f5a8fe on intridea:master.

[coveralls]

Changes Unknown when pulling 22340e4 on coletivoEITA:master into * on intridea:master*.

[pboling]

This is now handled in the current version of the code as follows:

    class AuthCode < Base
      # The required query parameters for the authorize URL
      #
      # @param [Hash] params additional query parameters
      def authorize_params(params = {})
        params.merge('response_type' => 'code', 'client_id' => @client.id)
      end

as per: https://tools.ietf.org/html/rfc6749#section-4.1.1