Uses protocol.ReconnectingClientFactory as superclass,
which uses exponential backoff in retrying.
Also change on_welcome_trigger callback to reset the
status of message channels which have reconnected,
so that they become operable once reconnected.
Also, some minor changes: filter_orders_callback taken outside
Taker since it involves user input necessarily. Related, answeryes
removed from module, can be done outside.
Donation code explicitly removed from all code branches for now.
A couple of very minor changes thrown up from testing.
Coverage of Taker now 100%, will work on the rest of jmclient.
Slight modification to install process, using pip install to avoid
polluting directories with build data.
Added general regression test support files to test/ (distinct from
planned package-level unit tests), this 2 levels of test should
function much better.