toy builder for GIO Thread Pool Performance tests

Change-Id: I1cdb99b2244095e244146fd31bd7da8dd2ebd8a6
Reviewed-on: http://review.couchbase.org/28609
Reviewed-by: Sundararaman Sridharan <sundar.sridharan@gmail.com>
Tested-by: Sundararaman Sridharan <sundar.sridharan@gmail.com>