Coinffeine/coinffeine — pull request #111 by sortega (2014-03-30 11:45:37+00:00)
Title: Make handshake arbiter notify the tx parts

**Description:** Make handshake arbiter notify the tx parts.

This change makes the handshake arbiter responsible for all
communications with the parts entering in an exchange so
is it easier to understand in isolation.

**Testing:** TDD