Set N Cilk Workers

[aanciaes]

Set environment variable CILK_NWORKERS to experiment with a different number of processors

[aanciaes]

Setting environment variable CILK_NWORKERS to 4 actually improved times from map and reduce
Run test environment with the following command:
docker run -it -v /path/to/cp/project:/mnt -e CILK_NWORKERS=4 aanciaes/cilkplus-pcre