Asynchronous session id generation

[soulman-is-good]

That's a project specific matter, but I have few of this projects that uses third-party unique generation mechanism, so I added a callback in session id generation.

Then I read #107 issue and tried to make it backward-compatible so sync functions would pass.

[dougwilson]

Thanks! It looks like there may be some issue, because one of the existing tests are failing.

[soulman-is-good]

My bad, missed the tests!

[dougwilson]

Man, if you never ran the tests, one failure is pretty good.

[dwhieb]

@soulman-is-good Thanks for tackling this! This is something I really need for a project myself. Will you have a chance to resolve the merge conflicts anytime soon?

[derMart]

would be really useful to have this...
+1

[dougwilson]

So I'm not sure what is happening, because the changes are all over the place. There is unresolved merge conflicts I see from a question a few months ago, and a lot of the things about the PR are not backwards compatible, so would need to be deferred until the next major.

I do need to come and review this, though, to at least prepare it for the next major. @soulman-is-good are you still interested in this PR? Would you be able to re-squash it on top of the current master for me?

[soulman-is-good]

Geez, seems I just f*cked up git's history here.

@dougwilson I can make another, clean and up-to-date, PR for this issue from your approval
Sorry for that.

[dougwilson]

Weird, not sure what happened with the PR :S I just had another user with a similar and resetting the branch completely fixed it, without ever needed to make a new PR.

Assuming the mess may be from merge commits if you merged instead of rebased, you may be able to fix it with the following commands (it assumes you have this repository set as the upstream remote):

$ git checkout master
$ git fetch upstream
$ git reset --hard upstream/master
$ git checkout -f . HEAD@{1}
$ git commit -a
# Validate your commit contents; "git reset --hard c19b52d" to abort
$ git push -f # if the commit looks good

[michelcve]

What happened with this one? I still think it's a good option to be able to asynchronously generete the session id...