https://github.com/spesmilo/sx/pull/78

I hope this can be merged.

I applied the patch to develop branch, but I think it's probably compatible
with master.

Clean separation between offline commands (not requiring connetion to
obelisk), and online commands, which talk to the blockchain.

This paves the path to future enhancements I have in mind, such as
separating between "watching" type commands and "signing" type commands,
following the electrum model. The end goal is to have a clean, user
friendly, command line based bip32 based wallet which cleanly splits
watching and signing functionality, and therefore can be used in high
security contexts just like electrum and armory.

Meanwhile, fun learning python and git flow :)