Request: add support for tokenKey

[stephenlacy]

Currently the JWT is added to the req.[requestKey].jwt.
I am requesting adding another option for setting the param jwt such as:

JWTSession({
  client: redis,
  secret: 'kat',
  requestKey: 'session',
  tokenKey: 'token'
})

// => req.session.token = JWT

I can send a PR to add the option along with tests.

[ricardogarim]

And if possible, add an option that keep the requestArg the same that was written (do not transform to 'x-some-thing' what was 'someThing'). What you think, @stevelacy?

[aembke]

That sounds like a good idea. I can shoot to get that added in the next week or so, or if you need it sooner feel free to submit a PR.

[aembke]

Was bored in a meeting, here's a PR that should take care of these.

#20

Feel free to give it a try on the feature branch and I'll push it to npm next week. I'm going to hold off on pushing it up for now pending some more complicated integration tests for the optional cookie support.

[aembke]

Now being tracked here: #21

[stephenlacy]

I tried it out, seems to be working well, thanks