Clojurians Log v2

fleshed this out some... it's shaping up nicely - https://github.com/mccraigmccraig/laters/tree/master/src/laters/control

PRW context will be very useful for async i think. it lets you pass environment into async computations, and keep a log, which will allow [1] log-context values and [2] something like a stacktrace