Threadpool size setting

ActiveRecord tends to really misbehave when run in threaded mode and not being careful with the connection pool. So on Rails when I run it in thread-safe mode I add middleware to grab a connection for each thread. The problem is with thin running on normal eventmachine that means I need a connection pool of 20 to mysql.
This let's you shrink down the number of eventmachine threads so you can have a smaller connection pool.