Non-blocking UDP in Tornado

[natronics]

Make tornado work with reading UDP sources so we don't have to manage threads ourselves.

[natronics]

Some examples to look at:

https://gist.github.com/robcowie/974695
http://kyle.graehl.org/coding/2012/12/07/tornado-udpstream.html
https://gist.github.com/jholster/2290574