Log Rotation: document or provide solution

## Problem

After a catchup on mainnet with log level `INFO`, the conduit log is more than 12GB. This is large enough that some sort of log rotation strategy is called for.

## Solution

We could either provide our own solution using a go library, or document how this could be done on various system. For example, on linux one could use [logrotate](https://www.digitalocean.com/community/tutorials/how-to-manage-logfiles-with-logrotate-on-ubuntu-16-04).

An argument for providing our own solution is platform independence, but a counter-argument is that this is non-standard.

## Dependencies

## Urgency

Low - I'm not sure how big of an issue this in the community