Fix #484

Ok this is a #484 fix.

Log.js does not take any time anymore (so it's not colored anymore \o/) but it's directly written in the file. We could discuss an option to remove date from the logs: 
if you use your own logging system an already got a date you'll have 2 in your pm2 logs. You could ofc write your own logs and not take any of pm2's log files.

I've removed the `dateformat` file because it's not needed anymore and wasn't really part of the script. Moment won't be required if `log-date-format` isn't specified.