Add slots pool module
Update process.start method to return it's pid
Add a bounded parrallel execution process pool
Update Process to support an on_exit callback
Quickfix select error call errno attribute reference
Fix dictionary iteration compat' with python3 in pool
Fix pool task id generation using uuid instead of urandom
Add a finish method to pool task
Update code documentation to explain potential OSError on semaphore acquire
Update slot pool to use Semaphore instead of BoundedSemaphore
Enhance code documentation
Fix slot release on method exception
Merge pull request #2 from botify-labs/feature/process_pool

Feature: process pool