Fixes#3457
Add `rake benchmark:run` task to run micro benchmark on specific part of
the code, it's uses the benchmark-ips gem to generate gem.
See https://github.com/evanphx/benchmark-ips for usage
This PR allow the Event class to compile a `sprintf` the first time and
reuse the template for the other calls. This strategy speeds up considerably
calls that uses date formatting or use fieldref its a bit slower if you
dont do any string manipulation.
Fixes#3425
