Separate logging output to own file

[joehand]

10:38 AM <•mafintosh> jhand: we should refactor the logger into a separate file in dat
10:39 AM <jhand> mafintosh: ya I've thought about that but couldn't quite see how it'd work. What were you thinking?
10:41 AM <•mafintosh> jhand: lets me a simple internal object in the dat folder that encapsulates the adding of files and stuff and emits events. not a js api - just something that encapsulates the js parts of it without logging anything
10:41 AM <•mafintosh> jhand: then we just listen for events and update the output
10:41 AM <•mafintosh> thats usually a cleaner
10:42 AM <jhand> mafintosh: ah ya. that makes sense. 
10:43 AM <•mafintosh> jhand: and the js event will be internal so its okay to just make it suit the internal needs and not make it a generic thing. it just shouldn't log anything
10:44 AM <jhand> mafintosh: ya, when I was thinking about it before it just seemed like going back to a JS API. but i guess we only need to support what we need. 
10:45 AM <•mafintosh> jhand: i have an example in old project i did here, https://github.com/mafintosh/hms
10:45 AM <•mafintosh> jhand: i have the js objects in the lib folder and then i add all the logs in the commands folder. no public js api

Will make #491 easier.

[joehand]

Starting this here: https://github.com/maxogden/dat/tree/logger-module

[joehand]

Starting this here: https://github.com/maxogden/dat/tree/logger-module