Fix hub brokenprocesspool (#136)
Fix hub brokenprocesspool (#136)

* Update manager.py
When scheduling a job to run in a separate process, it will check for if the process pool has crashed by submitting a simple job before submitting the real job, therefore preventing the need to restart the hub after a BrokenProcessPool has occurred.

* add notes and comments
Explains more parts of the `JobManager`
biothings/biothings.api,biothings/biothings.api