def sign_url(url, secret, opts = {})
      opts = default_opts.merge(opts)
      opts[:query_based] = true

      headers, url = *sign_request(url, secret, opts)
      url
    end
def sign_url(url, secret, opts = {})
      opts = default_opts.merge(opts)
      opts[:query_based] = true

      headers, url = *sign_request(url, secret, opts)
      url
    end
convienience method to sign a url for use with query-based authentication

 @param [String] url the url to sign
 @param [String] secret the secret used to sign the url
 @param [Hash] opts Options controlling the singature generation

 @option opts [String] :auth_param ('auth')    The name of the authentication param to use for query based authentication
 @option opts [Hash]   :extra_auth_params ({}) Additional parameters to inject in the auth parameter

 @return [String] The signed url