resolves #2

* added beak.threads modue
* the Runtime class now has a new attribute “thread_pool” which is a beak.threads.ThreadPool instance
* a BaseTarget now has a new attribute “_blocker” which is a beak.threads.BlockLock instance
* BaseTarget.execute_routine was modified to block until all threads that have been started with BaseTarget.run_thread have finished
* BaseTarget.run_thread was added
* the IOTarget.perform routine now implements parallelized builds
updated gcc resource script “optimize” function