This commit add testcases to test the following functions in bitcoin-tx:
- add a pay to non-standard script output
- add a P2SH output
- add a P2WSH output
- add a P2WSH wrapped in a P2SH output
- add a pay to pub key output
- add a P2WPKH output
- add a P2WPKH wrapped in a P2SH output
- add a bare multisig output
- add a multisig in P2SH output
- add a multisig in a P2WSH output
- add a multisig in a P2WSH wrapped in as P2SH output
