def save
      raise ArgumentError.new("Account is missing.") unless account
      
      account.require_secret
      
      hash = {}
      hash["settings"] = to_hash
      hash["secret"] = account.secret
      
      RippleRest.post "v1/accounts/#{account.address}/settings", hash
    end
def save
      raise ArgumentError.new("Account is missing.") unless account
      
      account.require_secret
      
      hash = {}
      hash["settings"] = to_hash
      hash["secret"] = account.secret
      
      RippleRest.post "v1/accounts/#{account.address}/settings", hash
    end
Save the account settings
 @raise [ArgumentError] if secret is missing from the Account object
 @raise [RippleRestError] if RippleRest server returns an error
 @raise [ProtocolError] if protocol is wrong or network is down
 @return [void]