Removed redundant requires

The master no longer requires worker or forking_execution_strategy since
they are required in lib/sisyphus.rb
Requiring a minimum ruby version fo 1.9.3
Added a spec_helper
The spec_helper
Moving requires around

Now it is possible to run the master_spec without making any extra requires
Extracted a WorkerPool class
Extracted the WorkerPool to its own file
Master has no @workers ivar..
Wrapped Master#create_worker

Getting ready to move create_worker from Master to WorkerPool