Strip colors from messages and metadata

It would be useful to strip out the color escape codes (i.e. `[33m`) from the logs sent to Logstash. It looks like Winston exposes a string transform we can use here to do this: https://github.com/flatiron/winston/blob/ea8bb5b7b2c58274dc128e1942846c8f1c9c19ae/lib/winston/common.js#L129. Would love to iterate on this if there is a better way; this is my first pass.
Merge pull request #18 from evNN/patch-1

Strip colors from messages and metadata