* rpcclient: Export sendCmd and response
This facilitates using custom commands with rpcclient.
See https://github.com/btcsuite/btcd/issues/1083
* rpcclient: Export receiveFuture
This facilitates using custom commands with rpcclient.
See https://github.com/btcsuite/btcd/issues/1083
* rpcclient: Add customcommand example
* rpcclient: remove "Namecoin" from customcommand readme heading