Identify functionality needs to be shared amongst tmpnb and tmpnb-redirector

[captainsafia]

Currently, both need the following and this should be moved to a separate library:

• [ ] CORS handling on all routes
• [ ] Command line options (some subset)

[minrk]

We could consider picking up tornado-cors to simplify some of the CORS config. Or we may want to build our own derivative/alternative package, but I'm not a fan of how many wheels we tend reinvent. @captainsafia do you want to investigate tornado-cors? The main thing we tend to support that tornado-cors doesn't is origin related:

• regexp-based origin checking
• server-side origin checking to enforce CORS for cases when headers aren't enough

[captainsafia]

Sure, @minrk. I'll look into tornado-cors a bit more and see what we can make from it.

[rgbkrk]

server-side origin checking to enforce CORS for cases when headers aren't enough

particularly when working with websockets