Add bitcoind zmq backend

[OttoAllmendinger]

• establish connection to bitcoind zmq socket
• listen for rawtx messages, deserialize and put into go channel
• listen for rawblock messages, deserialize and put into go channel

we could have multiple concurrent backends in the future (multiple nodes, other instances of bademeister)

[0xB10C]

I'd propose to do deserialization with the wire package from btcd. Have been using this without problems for the last few month.

[0xB10C]

I'd use defined types for the channels. Transaction and Block similar to:

• Transaction: wire.MsgTx and a fee as int64 (maybe embedd wire.MsgTx)
• Block: wire.MsgBlock

[OttoAllmendinger]

Implemented in https://github.com/0xB10C/bademeister-go/pull/14

• receive, parse vanilla hashtx
• receive rawblock

TODO:

• receive, parse extended notification containing vsize
• parse rawblock

[0xB10C]

• receive, parse extended notification containing vsize

19 implements parsing of the raw transactions and writes the tx weight (not vsize) to the database