Added logger and errorLogger with the help of 'winston' and 'express-winston'.
Writes by default to console in developer and a rotated log file in production.
Made log file name configurable.
The log is printed as json, so file extension should be .json, no need for dir and file when using Console
Merge pull request #43 from petteraas/express-winston-test

Added logger and errorLogger with the help of 'winston' and 'express-winston'
Set NODE_ENV to production when started with npm start