Improve multiprocessing #36
Description
- Make Simstock scripts run in parallel
- If possible, use imap since this could allow progress to be reported: https://stackoverflow.com/questions/5666576/show-the-progress-of-a-python-multiprocessing-pool-imap-unordered-call
- Reintroduce psutil
- Catch cases where number of available cores is either 0 or 1