TODO

SEGWIT-related
- create TxInputWitness class that includes the witness script and knows how to serialize itself and how to calc byte length (for get_vsize)
- segwit txs are valid but they are not identical to those that bitcoin core creates; there seems to be a difference in the signature calculation
  . this is because from bitcoin core v0.17 all signatures need to have low R (in addition to low S)
  . https://bitcoin.stackexchange.com/questions/88702/why-is-a-librarys-signature-of-a-segwit-tx-different-from-bitcoin-core-signatur
- tx serialization with no signed inputs produces a serialization which includes the 0001 segwit marker and thus is not identical to bitcoin core (the signed transaction is fine though) 
- witnesses=[] is initialized in Transaction class but still needed in the segwit testcases! -- check why and clean
  . redo testcases from scratch?!?!
- serialization of witnesses supports only script of size 252 and lower; that is because a simple len() is used instead of a compactSize/VarInt which allows up to 8 bytes of integers!
- explain get_transaction_segwit_digest() better and test further
- clean and comment the segwit examples !
  . test some more segwit txs including nested ones

TX-related
- should we use copy.deepcopy instead of the tx-related copy methods?

DOC-related
- add explicit documentation for each module before members...
- commit docs/usage/proxy.rst
- add segwit examples in README !
- segwit in documentation !?

CODE-related
- make all code < 80 chars !?

OTHERLIBS-related
- add to bitcoin-rpc lib option to ignore invalid ssl cert
  . needed to access remotely withut cert (for other validators from clients)
  . https://github.com/jgarzik/python-bitcoinrpc/pull/50
  . but not in a lib release yet
  . add config.ini option to optionally ignore cert so that it works when calling btcd remotely