Reviewer Matt - Add technical introduction document and create `doc` folder

Matt, this is the start of a technical write-up of Chronos (could become a logic manual in future possibly?).  It's basically a minor re-wording of what I sent to Adam back in January.  Can you please give it a once over?
"Our solution, Chronos..." implies that this is the first time you've called this Chronos but the text above uses this name repeatedly.