Format LogStash::Event for our purposes

I'm sure adding \n to the Event#to_s method is not the most universally friendly way to put newlines on rails console output, but it certainly does the trick.

Also since we are stringifying time in our gem, which I can't really find a solid case for on my side, we have to take the iso8601 call out of Event#to_s since it doesn't make sense to call 
````
"2014-05-29T10:21:38.086+00:00".iso8601
```