Add initial source, docs

This PR adds an initial version of `cee-format`.  This allows us to produce log output structured in the standard [CEE format](https://fedorahosted.org/lumberjack/), rather than having to log out custom strings, which are not easily parsable by anybody.  CEE on the other hand, is both parsable by standard logging infrastructure such as `rsyslog`, and, being JSON based, the output can then be passed on to nearly anybody for standardized parsing, storage, etc.

This doesn't talk directly to a logger like `timbre` or to `syslog` itself, it just converts the data.  Further/other work can handle those concerns, once we can produce the data itself.