[BUG] !Important - Tornado breaks jupyter notebooks OR Mesa

[jackiekazil]

See: #489
... but current version now breaks tornado/Mesa. :-(

I will look through this tonight/this weekend to see if there is a comprise version to hold both things together or if I can fix Mesa.

Whatever solution I come with, I will be looking for a fast merge into master to resolve this.
If you see this ticket and have time to pick up before I do, please do and document in the ticket.

To recreate...

• To break jupyter, install tornado==4.0.2 and run a notebook to see Kernal die.
• To break tornado / Mesa, run pip install tornado and run Schelling to get ioloop error.