Wireless sensor nodes update

My wireless sensor nodes have been in need of a little TLC for a few months.  One of them is still going strong (after 3 years on a single coin cell!) but the other two need a replacement battery and the server stopped working after an Ubuntu upgrade.

To fix the server I've reworked the code to turn it into a more proper python package and updated the instruction to use upstart rather than monit, which I found to be too complex for its own good.

Interestingly, it looks like the nodes that needed a new battery starting reading bad temperature data before they stopped transmitting.  I'd have expected transmission to be the first thing to go, given how much power it requires.