Compatibility with Tornado 5.0

[rolweber]

Our unit tests are failing with Tornado 5.0, as exposed by PR #280.

http://www.tornadoweb.org/en/stable/releases/v5.0.0.html

[rolweber]

A cheap trick would be to require Tornado<5.0a. But we should rather ensure that the unit tests and KG itself work with Tornado 5.0.

[kevin-bates]

We see the same issue in Enterprise Gateway (of course) and have documented it in JEG 278. In the meantime, we updated the build to limit Tornado versions to < 5.0 so as to reduce the noise on regular PR traffic.

Another primary change is the removal of the ioloop parameter from various methods - which is why updates to jupyter_client and notebook (et al) are referenced in the link.