add support for size based log rotation
Merge pull request #344 from jespada/sizebased-logrotation

add support for size based log rotation
streams/batch: batch up events in space and time.

Especially useful for folks having performance issues with IO; for
instance, the librato metrics client can accept a vector of events and
will make a single HTTP request for the entire vector as a batch.
Merge branch 'master' of github.com:aphyr/riemann
Fix ns collisions for streams.batch