def update(address, new_address, options={})
      params = {:address => new_address}
      Mailgun.submit :put, list_url(address), params.merge(options)
    end
def update(address, new_address, options={})
      params = {:address => new_address}
      Mailgun.submit :put, list_url(address), params.merge(options)
    end
Update a mailing list with a given address
 with an optional new address, name or description