message: Add BCH testnet network properties
  Summary: The BCH testnet does not vary much from the BTC testnet, but the coin property needs to be updated to 'BCH'. This is what caused the SDK BCH transaction tests to fail.
  Reviewers: kevin, arik, zacleids
diff: @@ -16,6 +16,18 @@ module.exports = {
  coin: coins.BCH,
  forkId: 0x00
  },
  + bitcoincashTestnet: {
  + messagePrefix: '\x18Bitcoin Signed Message:\n',
  + bech32: 'tb',
  + bip32: {
  + public: 0x043587cf,
  + private: 0x04358394
  + },
  + pubKeyHash: 0x6f,
  + scriptHash: 0xc4,
  + wif: 0xef,
  + coin: coins.BCH
  + },
  zcash: {
  messagePrefix: '\x18ZCash Signed Message:\n',
  bech32: 'bc',
  