Change how log line limits drop lines

[duanemay]

This PR is to update the docs to reflect new behavior for the beta log-rate-limit feature.

Previously, Diego was placing logs into a buffer and releasing them in accordance with the log line limit that was set. If the limit is exceeded, logs would be delayed. If the buffer overflowed, logs would be dropped. The new behavior is to immediately output logs without placing them into a buffer. When the limit is reached, logs are dropped. This change makes the timestamps of logs match when they were actually output by the app.

[cf-gitbot]

We have created an issue in Pivotal Tracker to manage this. Unfortunately, the Pivotal Tracker project is private so you may be unable to view the contents of the story.

The labels on this github issue will be updated when the story is started.