tornado 5+ support

[toddrme2178]

This package requires tornado 4. However, tornado 4 will stop working with Python 3.8. Tornado 5 was released March 2018 and Tornado 6 was release March 2019. Both will work with Python 3.8. Would it be possible to update this package to work with at least tornado 5 and ideally both tornado 5 and 6 so it can be used with Python 3.8? Thank you.

[dahlia]

Sorry, but I currently have no much spare time to fix this, and no enough experience about Tornado. However, if you would like to send a patch to fix this, I am going to review that as soon as possible.