message: Fix TLTC network
  The LitecoinTestnet class extended Mainnet ... it should extend Testnet
  instead.
diff: @@ -82,7 +82,7 @@ class Litecoin extends Mainnet implements UtxoNetwork {
  family = CoinFamily.LTC;
  }
  -class LitecoinTestnet extends Mainnet implements UtxoNetwork {
  +class LitecoinTestnet extends Testnet implements UtxoNetwork {
  bech32 = 'tltc';
  // clarify these constants - they are different between BitGoJS and bitgo-utxo-lib
  bip32 = {
  