Use ZMQ events when using bitcoind

[tiero]

It closes #267

[tiero]

I have a problem using a local node with http instead of https: it wont work unless you patch btcd method!

// NewBitcoindConn creates a client connection to the node described by the host
// string. The ZMQ connections are established immediately to ensure liveness.
// If the remote node does not operate on the same bitcoin network as described
// by the passed chain parameters, the connection will be disconnected.
func NewBitcoindConn(cfg *BitcoindConfig) (*BitcoindConn, error) {
	clientCfg := &rpcclient.ConnConfig{
		Host:                 cfg.Host,
		User:                 cfg.User,
		Pass:                 cfg.Pass,
		DisableAutoReconnect: false,
		DisableConnectOnNew:  true,
		DisableTLS:           **true**,
		HTTPPostMode:         true,
		Params:               cfg.ChainParams.Name,
	}